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PUBLISHED BY 

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Examination of Milk for Public Health 
Purposes. 

A practical handbook for those engaged In 
the chemical and bacteriological examination 
of milk for public health purposes, vi + 224 
pages, 5i X 8, 4 diagrams. Cloth, $1.75 net. 

Chlorination of Water. 

In this book the various aspects and methods 
of chlorination are discussed with a view to 
stimulating research work in this field of 
science, viii + 158 pages, 5J X 8, 12 figures 
and 16 diagrams. Cloth, $1.50 net. 



Chlorination of Water 



BY 

JOSEPH RACE, F.I.C. 

City Bacteriologist and Chemist, Ottawa; Capt. Canadian Army Hydrological Co?ps; 

Associate Member of Committee on Water Supplies, American Public Health 

Association; Af ember of Committee on Water Standards a?id Standard 

Methods of Analysis, American Water Works Association; 

Chairman of Committee on Standard Methods of 

Analysis, Canadian Public Health Association 



FIRST EDITION 



NEW YORK 

JOHN WILEY & SONS, Inc. 

London: CHAPMAN & HALL, Limited 
1918 






Copyright, 1918 

BY 

JOSEPH RACE, F.I.C. 



NOV 20 1918 



PRESS OF 

BRAUNWORTrt & CO. 

>OOK MANUFACTURER! 

BROOKLYN. N. V. 



©CI.A506648 \$^ Q$ fr 



DEDICATED 

TO 

#ir ^lexanter fmtshm, %$&., P.&e., M-W» <&-M 



PREFACE 



No apology is necessary for the publication of a book 
on the chlorination of water. This method of treatment, 
practically unknown fifteen years ago, has advanced in 
popularity during the last decade in a most remarkable 
manner, and in 19 18 over forty millions of people are being 
supplied with chlorinated water. 

It may justifiably be said that no other sanitary measure 
has accomplished so much at so small a cost; and that 
civilization owes a deep debt of gratitude to the pioneers 
in municipal water chlorination: Dr. A. C. Houston in Eng- 
land, and Mr. G. A. Johnson and Dr. Leal in America. 

In this volume I have endeavoured to collect and cor- 
relate the information hitherto scattered in various journals 
and treatises and to present it in a comprehensible manner. 
The various aspects and methods of chlorination are dis- 
cussed and suggestions have been made which, I hope, 
will stimulate research work in this fertile field of science. 

I wish to acknowledge my indebtedness to the engineer- 
ing staff of the Ottawa Water Works Department and to 
Lieut. W. M. Bryce for the preparation of diagrams. 

Joseph Race. 

Ottawa, Ont., 
April, 191 8. 

V 



CONTENTS 



I. Historical i 

Sodium Chloride. Chlorine. Bleach. Eau de Javelle. 
Antiseptics. Hermite fluid. Webster's process. Elec- 
trozone. Chlorination of sewage in Germany, U. S. A., 
and England. Chlorination of water. Lincoln installa- 
tion. Oxychloride. German experiments. European 
practice. Inception of chlorination in America. 

II. Modus Operandi 14 

Composition of bleach. Bleaching action. Nascent 
oxygen hypothesis. Hydrolysis of bleach. Effect of acids 
and salts on hydrolysis and germicidal action. Effect of 
ammonia. Direct toxic action. Hypochlorous acid. 
Sodium hypochlorite. Chlorine water. Nature of action. 

III. Dosage 30 

Organic matter. Initial count. Viability of organisms. 
Mineral matter. Colour. Temperature. Admixture. 
Contact period. Turbidity. Light. Determination of 
dosage. 

IV. Bacteria Surviving Chlorination 50 

Disinfectants. Antiseptics. Viability of bacteria. New 
York results. Reversed ratio of counts. Coliform organ- 
isms. Aftergrowths in water and sand. 

V. Complaints 62 

Auto-suggestion. Tastes and odours. Sludge problem. 
Colic. Effect on fish and birds. Effect on plants and 
flowers. Corrosion of iron and lead pipes. 



viii CONTENTS 

CHAPTER PAGE 

VI. Bleach Treatment 72 

Storage of bleach. Mixing tanks. Storage tanks. Dos- 
ing apparatus. Control. Analysis of liquor. Detection 
and estimation of free chlorine. Chlorometer. Cost of 
construction and operation. Antichlors. DeChlor niters. 

VII. Liquid Chlorine . . 89 

Historical. Leavitt-Jackson machine. Electro Bleach- 
ing Gas Co.'s types. Wallace and Tiernan's manual con- 
trol types. Effect of temperature on gas pressure. Im- 
purities in gas. Advantages. Comparison of liquid 
chlorine and bleach. Cost of treatment. Popularity. 
Chlorine water. 

VIII. Electrolytic Chlorine and Hypochlorites 105 

Hermite fluid. Eau de Javelle. Chloros. Non-dia- 
phragm cells: Dayton, Hermite, Mather and Piatt, Haas 
and Oettel. Diaphragm cells: Hargreaves-Bird, Nelson, 
Allen-Moore. Montreal installation. Costs. 

IX. Chloramine 115 

Preparation. Absorption by water. Experimental 
results. Works results. Ratio of chlorine to ammonia. 
Economics. Advantages. Operation. Other chlora- 
mines. Halazone. 

X. Results Obtained 132 

Object of chlorination. Effect on filter rates and algae. 
Hygienic results. Typhoid rates. Typhoid reduction at 
Philadelphia, Chicago, and Ottawa. Abortive epidemics. 
Use and abuse of chlorination. 

Appendix 147 

Estimation of free chlorine in water. 

Name Index 151 

Subject Index 155 



CHLORINATION OF WATER 



CHAPTER I 
HISTORICAL 

Chlorine, although one of the most widely distributed 
elements known to chemists, is never found in the free con- 
dition in nature; it exists in enormous quantities in com- 
bination with sodium, potassium, calcium, magnesium, etc. 
As sodium chloride, common salt, it occurs in practically 
inexhaustible quantities in sea water together with smaller 
quantities of other chlorides. In mineral form, enormous 
deposits of sodium chloride are found in Galicia, Transyl- 
vania, Spain, in England (particularly in Cheshire), and in 
sections of North America. The most important deposits 
of potassium chloride are those at Stassfurt, Germany, 
where it occurs either in the crystalline condition as sylvine 
or combined with magnesium chloride as carnallite. 

Chlorine was discovered by the Swedish chemist Scheele 
in 1774, but he, like Lavoisier and his pupil Berthollet, who 
declared it an oxygenated muriatic acid, was unaware of 
the elemental nature of the new substance. Sir Humphrey 
Davy investigated this body in 1810 and definitely proved 
it to be an element; Davy designated the element chlorine 
from the Greek x^P°s = green. 

The first attempt to utilise chlorine, or its compounds, 



2 CHLORINATION OF WATER 

for bleaching purposes, appears to have been due to James 
Watt, who noticed the decolourising properties of chlorine 
during a visit to Berthollet. This attempt ended in failure 
because of the destructive effect on the fibres, but, in later 
trials, this was prevented by first absorbing the gas in a 
solution of fixed alkali. These experiments proved the 
possibility of bleaching by means of chlorine compounds 
but the high cost of soda made the process unprofitable, 
and it was not until Henry succeeded in preparing a com- 
bination with lime that could be reduced to a dry powder 
that this mode of chemical bleaching became a commercial 
success. 

The manufacture of chloride of lime (hypochlorite of 
lime, bleaching powder, bleach) was taken up by Charles 
Tennant in 1799 at St. Rollox near Glasgow, and in 1800 
about 50 tons were sold at a price of $680 (£139) per ton. 

Chlorine is produced as a by-product in the manufacture 
of soda by the Leblanc process, but until 1865, when the 
British Alkali Act stopped the discharge of hydrochloric 
acid vapours into the atmosphere, the development of the 
bleaching powder industry was not rapid. The hydro- 
chloric acid that was formerly discharged into the air as a 
waste product afterwards became a valuable asset that 
enabled the Leblanc process to successfully compete with 
the newer ammonia-soda process. In 1890 another com- 
petitor to the Leblanc process was introduced when caustic 
and chlorine were produced in Germany by electrolytic 
methods. After the successful development of this method 
in Germany, it was taken up in the United States of America 
and in 191 2 more than 30,000 electrical horse-power were 
daily used in this industry. In 1914 the almost complete 
cessation of exports of bleach from Europe raised the price, 
which attained phenomenal heights in 191 6 (cf. page 
125), and stimulated the production of bleach both in the 
U. S. A. and Canada. 



HISTORICAL 



TABLE I.— BLEACH STATISTICS. NORTH AMERICA 



Year. 


Bleach Manufactured, 
Short Tons. 


Selling Price Per 100 Lbs. 


1904 


19,000 




1909 


58,000 




1914 


155,000 


$1.63 


1915 


180,000* 


2.63 


1916 


230,000* 


6.56 


1917 


260,000* 


2.44 



* Estimated. 

As a disinfectant, chlorine was first used about the year 
1800 by de Morveau, in France, and by Cruikshank, in 
England, who prepared the gas by heating a mixture of 
hydrochloric acid and potassium bichromate or pyrolusite; 
this is essentially the same as the original mixture used by 
Scheele. 

During the early part of the last century the efficacy 
of chlorine of lime as a disinfectant, and particularly as a 
deodourant, was well recognised and as early as 1854 an 
English Royal Commission used this substance for deo- 
dourising the sewage of London. A committee of the 
American Public Health Association reported in 1885 that 
chloride of lime was the best disinfectant available when 
cost and efficiency were considered. 

Eau de Javelle, first made by Percy at the Javelle works 
near Paris in 1792. is another chlorine compound that has 
enjoyed a considerable reputation as a disinfectant and 
deodouriser for over a century; it is essentially a mixture 
of sodium chloride and sodium hypochlorite. 

The discovery of electrolytic hypochlorites dates back 
to 1859, when Watt found that chlorides of the fixed alkalies 
and alkaline earths yielded hypochlorites on being sub- 
mitted to the action of an electrical current. 

Until the middle of the last century disinfection was 
regarded as a process that arrested or prevented putrefac- 



4 CHLORINATION OF WATER 

tive changes but the nature of these changes was imperfectly 
comprehended and micro-organisms were not associated 
with them. 

In 1839 Theodor Schwann, 1 who might be regarded as 
the founder of the school of antiseptics, reported that "Fer- 
mentation is arrested by any influence capable of killing 
fungi, especially by heat, potassium arseniate, etc. . . ."; 
but his results were not accepted by the adherents of the 
theory of spontaneous generation and it was not until the 
publication of the work of Schroder and Dusch 2 that 
Schwann's views were even partially accepted. The final 
refutation to the spontaneous generation theory was given 
by the monumental researches of Pasteur who, in 1862, 
proved the possibility of preparing sterile culture media 
and demonstrated the manner in which they could be 
protected from contamination. Bacteria and other micro- 
organisms were shown to be responsible for the phenomena 
that had been attributed previously to the " oxygen of the 
air," and from this period the development of bacteriology 
as a science proceeded rapidly. 

The next important step, from the public health stand- 
point, was the discovery by Kochj in 1876, that a specific 
bacterium (B. anthracis) was the cause of a specific disease 
in cattle (anthrax or splenic fever). In 1882 Koch made 
a further advance by developing a solid culture medium 
which permitted disinfectants and antiseptics to be studied 
quantitatively with a greater degree of accuracy than had 
been possible previously. 

Since 1845, when Semmelweiss succeeded in stamping 
out puerperal fever in Vienna, where it had been so long 
established as to be endemic, chlorine has been very generally 
employed in sanitary work and the conditions necessary 
for obtaining successful results have been partially eluci- 
dated. Baxter was the first to state that the disinfecting 
action depended more upon the nature of the pabulum than 



HISTORICAL 5 

upon the specific organism present and this was confirmed 
later by Kuhn, Bucholtz, and Haberkorn. The latter 
found that urine consumed large quantities of chlorine 
before any disinfection occurred. 

One of the earliest preparations used in sanitary work 
was an electrolysed sea water, usually known as Hermite 
Fluid. This was introduced by M. Hermite in 1889 and 
was employed for domestic purposes and for flushing sewers 
and latrines. It was used at Brest for the dissolution of 
faecal matter and a prolonged trial was given to it at 
Worthing in 1894. The report of Dupre and Klein, who 
conducted the bacteriological examinations, was against the 
process, but Ruffer and Roscoe reported more favourably 
and further trials were carried out at Havre, l'Orient, and 
Nice. The Lancet (May 26, 1894) reported at length upon 
the Worthing experiments: it was found that during the 
electrolysis of the sea water, the magnesium chloride was 
also partially converted into hypochlorite, which then dis- 
sociated into magnesium hydrate and hypochlorous acid; 
the former deposited in the electrolyser and left the solu- 
tion acid and unstable; urine was found to act upon it at 
once with a consequent loss in strength of over 50 per cent. 

Another electrolytic method was that of Webster, 3 who 
installed an experimental plant at Crossness, near London, 
in 1889. A low-tension direct current was passed between 
iron electrodes placed in the sewage and although the process 
was largely one of chemical precipitation, Webster noted 
the disinfecting value of the hypochlorite formed from the 
chlorides normally present in the sewage. He also directed 
the attention of sanitarians to the possibility of using sea 
water as a cheap source of chlorides and a plant based on 
this principle was erected in Bradford in 1890 and reported 
upon by McLintock. 4 

Strong salt solutions were substituted for sea water by 
Woolf and the product was commercially known as "Elec- 



6 CHLORINATION OF WATER 

trozone." A plant of this description was installed at 
Brewster, N. Y., in 1893 5 for chlorinating the sewage from 
a small group of houses. The sewage was discharged into 
a small creek which polluted Croton Lake. Successful 
results led to a similar treatment near Tonnetta Creek. 6 
This was apparently the first occasion on which the spe- 
cific object was the destruction of bacteria. 

Electrozone was used at Maidenhead, on the Thames, 
in 1897 and the installation was reported upon by Robin- 
son, Kanthack, and Rideal in 1898. Kanthack found that 
a dosage 3-3.6 p.p.m. reduced the organisms in a sewage 
effluent to 10-50 per c.cm. whilst Rideal found that about 
18 p.p.m. of chlorine produced a condition of sterility in 
1 c.cm. 

Chloride of lime had previously been used in the Lon- 
don sewage as a deodourant by Dibden in 1884 but the 
treatment was not successful and was abandoned in favour 
of other oxidisers. 

During the last decade of the twentieth century the use 
of bleach for the disinfection of both sewage and water 
received the attention of many well-known German sani- 
tarians and many important results were obtained. 

In the earlier experiments made at Hamburg, Proskauer 
and Eisner 7 obtained satisfactory results with 3-4 p.p.m. 
of chlorine on a clarified sewage with 10 minutes contact. 
Dunbar and Zirn (ibid.) used crude sewage and found that 
17 p.p.m. of available chlorine were required to remove 
B. typhosus and cholera vibria with a contact period of two 
hours. A striking feature of all the German work on chlori- 
nation is the very high degree of purification aimed at: 
quantities as large as one litre were tested for specific organ- 
isms and in many of the experiments with sewage B. coli 
was found to be absent from a considerable percentage of 
the samples. 

The importance of previously removing suspended mat- 



HISTORICAL 7 

ter, which could not.be penetrated by the germicide, was 
emphasised by Schwartz 8 although it had been previously 
noted by Schumacher. 

At the Royal Testing Station in Berlin, numerous experi- 
ments on sewage chlorination were made by Kranejuhl 
and Kurpjuivut. 9 The results were judged by the B. coli 
content, which was taken as an index of pathogenicity 
because this typical intestinal bacillus was found to be more 
frequent and less viable than the majority of the patho- 
genic organisms. 

Other important work on this subject was carried out, 
in connection with the pollution of the Hooghly River, by a 
Bengal Government Commission in 1904; and by the State 
Board of Health of Ohio in co-operation with the Bureau 
of Plant Industry of the United States Department of 
Agriculture in 1907. The chlorination experiments of the 
latter were reported by Kellerman, Pratt, and Kimberly. 10 

The most valuable contribution to the disinfection of 
sewage was that of Phelps, 11 who critically examined the 
work of previous experimenters and directed attention to 
the unnecessary stringent standards adopted in European 
practice. His work at Boston in 1906, at Red Bank, N. J , 
and at Baltimore in 1907, demonstrated in an indubitable 
manner the economic possibilities of sewage chlorination. 
The dosages necessary for crude sewage and filter effluents 
were indicated and also the necessary contact periods. 
This work marks the commencement of a new era in sanitary 
science. 

The first occasion on which chlorine compounds were 
first used for the disinfection of water cannot be definitely 
ascertained. It has been stated to the author that bleach 
was used for treating wells as early as 1850 but this treat- 
ment was apparently made without definite knowledge of 
the destruction of micro-organisms. 

In 1897, Sims Woodhead employed bleach solutions for 



8 CHLORINATION OF WATER 

the sterilisation of the distribution mains at M aidstone, 
Kent, subsequent to an epidemic of typhoid fever. 

The credit for the first systematic use of chlorine in water 
disinfection is due to A. C. Houston with whom McGowan 
was associated in the work carried out at Lincoln in 1904- 
1905. 12 The reservoirs, filters, and distribution system, 
owing to flood conditions, became infected with typhoid 
bacilli which caused a severe epidemic amongst the con- 
sumers. The storage and purifications works were thor- 
oughly treated with a solution of "chloros" (sodium hypo- 
chlorite containing approximately 10 per cent of available 
chlorine) which was regulated to give an approximate dosage 
of 1 part per million. The bacteriological results were 
entirely satisfactory but many complaints were received 
that the treatment had imparted a mawkish taste to the 
water. This was attributed to the action of the alkaline 
chloros on the organic impurities in the water. It was also 
stated that the water injured plants, fish, and birds and 
extracted abnormal amounts of tannin from tea but no 
substantiating evidence was produced in support of these 
complaints. Houston made a continuous physiological test 
of the effect of the chlorinated water, on small fish by sus- 
pending a cage of gold fish in the filter effluent chamber 
and also proved that the treatment had no appreciable 
effect on the plumbo-solvency of the supply. 

Nesfield, of the Indian Army Medical Service, 13 reported 
in 1903 the results of numerous experiments on the destruc- 
tion of pathogenic organisms by chlorine compounds and 
suggested their use in military work to prevent a recurrence 
of the appalling loss of life from water-borne diseases 
(especially enteric fever) such as took place during the 
Boer War. Nesfield proposed to use about 100 p.p.m. of 
available chlorine and to remove the excess after a contact 
period of 10 minutes. This work is especially interesting 
from the historical standpoint because it contains the first 



HISTORICAL 9 

suggestion of the possibilities of compressed chlorine gas 
in steel cylinders. 

A few years later, electrolytic hypochlorite (oxychloride) 
was used at Guildford by Rideal and various chlorine com- 
pounds were tried on the water of the Seine and Vanne, in 
France, and at Middlekerke and Ostend, in Belgium. 
Experimental work on water chlorination was also reported 
by Thresh and by Moor and Hewlett. 14 

During the nineties many experiments on water chlori- 
nation were made by Traube. Sickenberger, Kauffman, 
Berge, Bassenge, and others. Traube 15 was able to com- 
pletely sterilise water rich in bacteria in 2 hours by the 
addition of bleach equal to 1.06 p.p.m. of available chlorine. 
At the end of the contact period about 90 per cent of the 
added chlorine was unabsorbed and was destroyed by the 
addition of sodium bisulphite. Bassenge 16 followed up the 
work of Traube and that of Sickenberger and Kauffman, 
who had shown that it was possible to destroy cholera 
vibrio in Nile water by means of sodium hypochlorite. 
Bassenge used higher concentrations than Traube and found 
it possible to destroy B. typhosus and B. coli in ten minutes 
with 60-90 p.p.m. of available chlorine. The excess was 
destroyed by adding calcium bisulphite. Lode 17 experi- 
mented with waters seeded with B. coli, B. typhosus, and 
B. tetani and found, contrary to Traube, that 1-2 p.p.m. 
of chlorine did not sterilise in two hours. B. coli was usually 
destroyed by 4 p.p.m. of chlorine in ten minutes and even 
better results were obtained with B. typhosus and cholera 
vibrio: the former was destroyed in one hour by 1 p.p.m. 
and in ten minutes by 2 p.p.m.; the latter organism required 
1-2 p.p.m. with a twenty-minute contact period. Lode 
noted that organic matter lowered the bactericidal activity 
of chlorine and recommended the use of 30 p.p.m. of chlorine 
to ensure rapid and complete sterilisation. Berge 18 used 
chlorine peroxide, generated by the action of hydrochloric 



10 CHLORINATION OF WATER 

acid on potassium chlorate, for the sterilisation of water 
and this process was afterwards used at Ostend at a plant 
having a capacity of about 1,300,000 gallons per day. The 
dosage was equal to 0.53 p.p.m. of available chlorine and 
coke niters were used to destroy the excess although they 
were not found to be indispensable as the free chlorine 
disappeared spontaneously. This process appears to have 
been tried on the Brussels supply and also for the treatment 
of a hospital supply at Petrograd. 

The object of German sanitarians seems to have been 
to obtain practically instantaneous sterilisation of water 
for the use of travellers and troops in the field. Until the 
commencement of the European War they did not have a 
high opinion of chlorination and generally regarded it as 
inefficient. Schumberg i9 expressed the opinion that no 
chemical method of disinfection could be absolutely relied 
upon, under all circumstances, to prove fatal to bacteria. 
Plucker 20 stated that several investigators, particularly 
Schuder, had shown that chlorine, even in the proportion of 
40 p.p.m. did not invariably destroy cholera vibrio and B. 
typhosus) and that with smaller doses the destruction 
was still less complete. He also stated that the bacterio- 
logical experiments of American workers were open to 
criticism and that they employed antiquated methods. 

By 1916 the German sanitarians appeared to have realised 
that their bacteriological standards were too stringent 
(Langer 21 ) and that the process had proved its value in an 
indisputable manner. 

European practice, in the comparatively few instances 
in which it has been used, has been to employ large doses 
of chlorine and to remove the excess by chemicals or by 
filtration through special media. In 191 6, however, Lon- 
don commenced to chlorinate a portion of its supply and the 
following year practically the whole supply was chlori- 
nated. A dosage of approximately 0.5 p.p.m. is used and 



HISTORICAL 11 

the bleach solution is added to the pre-filtered water. Worces- 
ter is also proposing to chlorinate the supply to main- 
tain the purity of the water without extending the slow sand 
nitration plant. 

In North America, hypochlorite of soda and chlorine 
were used on the Jewell Filter at the Louisville Experimental 
Station in about 1896 by George W. Fuller and a year later 
they were used at Adrian by Jewell. The first commercial 
successful attempt was made by G. A. Johnson. In 1908 
the Union Stock Yards Company of Chicago were proceeded 
against by the City of Chicago regarding the condition of the 
effluent of the Bubbly Creek filter plant. Copper sulphate 
had been previously used in conjunction with the filters 
but stock shippers complained that the water had a deleteri- 
ous effect upon the animals consuming it. Johnson elimi- 
nated the copper treatment and substituted bleach which 
was added seven and a half hours previous to filtration, with 
a dosage of 1.5 p.p.m. The results were very satisfactory. 

About the same time, Johnson and Leal commenced the 
treatment of the Boonton supply of Jersey City, N. J., which 
consumed about 40 million gallons per day. The water was 
first treated with 36 pounds of bleach per million gallons 
(1.4 p.p.m. of available chlorine) but this quantity was 
gradually reduced until only 5 pounds per million gallons 
(0.2 p.p.m. of chlorine) were being used in April, 1909. 
The ability of the process to adequately purify water became 
the cause of a lawsuit and the decision of the Court 
was: 

"From the proofs taken before me, of the constant obser- 
vation of the effect of this device, I am of the opinion and 
find that it is an effective process which destroys in the water 
the germs, the presence of which is deemed to indicate 
danger, including the pathogenic germs, so that the water 
after this treatment attains a purity much beyond that 
attained in water supplies of other municipalities. The 



12 CHLORINATION OF WATER 

reduction and practical elimination of such germs from the 
water was shown to be substantially continuous. 

"Upon the proofs before me, I find that the solution 
described leaves no deleterious substances in the water. 
It does produce a slight increase in the hardness but the 
increase is so slight as in my judgment to be negligible. 

"I do therefore find and report that this device is capable 
of rendering the water delivered in Jersey City pure and 
wholesome, for the purposes for which it is intended and is 
effective in removing from the water those dangerous germs 
which were deemed by the decree to possibly exist therein 
at certain times." 22 

During the next few years the use of hypochlorite in 
water purification, both alone and in conjunction with 
nitration, became very popular and in 191 1 over 800 million 
gallons per day were treated in this manner. Amongst the 
users were some of the largest cities in North America, 
including Brooklyn, Albany, and New York City, N. Y., 
Cincinnati and Columbus, Ohio, Harrisburg, Philadelphia, 
Pittsburg, and Erie, Pa., Hartford, Conn., Nashville, Tenn., 
St. Louis and Kansas City, Mo., Montreal, P. Q., Toronto 
and Ottawa, Ont., Baltimore, Md., and Minneapolis, Minn. 
At present (191 8) over 3,000 million gallons per day are being 
chlorinated in North America and more than 1,000 cities 
and towns are employing this process. 

BIBLIOGRAPHY 

(1) Schwann. Microskopische Untersuchungen iiber die Ubereinstim- 

mung in der Textur und dem Wachstum der Tiere und Pflanzen. 
Berlin. 1839 

(2) Schroder and Dusch. Ann. der Chem. u. Pharm., 1854, 89, 232. 

(3) Webster. The Engineer. 1889, 67, 261. 

(4) McLintock. Brit. Med. Jour., 1890, 11, 498. 

(5) Eng. News. 1893, 30, 41. 

(6) Eng. Record. 1894, 29, no. 



HISTORICAL 13 

(7) Proskauer and Eisner. Vierteljahreschr. ger. Med. ii. off. San- 

itatswesen. 1898, 16, Supp. Heft. 

(8) Schwartz. Gas. Eng., 1906, 29, 773. 

(9) Kranejuhl and Kurjuivut. Mitteilungen aus der Koniglichen 

Priifungsanstalt fiir Wasserversorgung und Abwasserbeseitigung 
zu Berlin, 1907, 9, 149. 

(10) Kellerman, Pratt, and Kimberly. Bull. 115, Bur. Plant Ind., 

U. S. Dept. of Agr., 1907. 

(11) Phelps. Water Supply Paper 229, Dept. of Int., U. S. Geo. Survey. 

(12) Houston and McGowan. 5th Rpt. Royal Commission on Sewage 

Disposal. 

(13) Nesfield. Public Health. 1903, 15, 601. 

(14) Moor and Hewlett. Rpt. of M. O. to L. G. B., 1909-10. 

(15) Traube. Zeit. f. Hyg., 1894, 16, 149. 

(16) Bassenge. Zeit. f. Hyg., 1895, 2 °> 22 7- 

(17) Lode. Archiv. f. Hyg., 1895, 24, 236. 

(18) Berge. Rev. d'Hyg., 1900, 22, 905. 

(19) Schumburg. Zeit. f. Hyg., 1903, 45, 125. 

(20) Plucker. J. Gasbeleucht., 191 1, 54, 385. 

(21) Langer. Zeit. f. Hyg., 1916, 81, 296. 

(22) Johnson. Jour. Amer. Pub. Health Assoc, 191 1, 1, 566. 



CHAPTER II 



MODUS OPERANDI 



Before considering the "modus operandi" of chlorine 
and hypochlorites it will be advisable to take up the com- 
position of the latter substances and particularly that of 
" bleach." Bleach is manufactured by passing chlorine 
gas over slaked lime and the ensuing reactions are often 
represented by the equation Ca(OH)2 + Cl2 = CaOCl2+H20. 
This represents the substance formed as a pure oxychloride 
of calcium which contains approximately 50 per cent of 
chlorine, but the article commercially produced never con- 
tains this amount of chlorine, the usual percentage being 
from 35-37. The general composition of commercial bleach 
is fairly uniform. This is shown in the following analyses of 
which two are of German bleach examined by Lunge, and 
one of Canadian manufacture analysed by the authors 



Available chlorine 

Chlorine as chlorides . . . 
Chlorine as chlorates . . . 

Lime 

Magnesia 

Iron oxide 

Alumina 

Carbon dioxide 

Silica 

Water and undetermined 



Lunge. 


% 


% 


37.OO 


38.30 


°-35 


°-59 


0.25 


0.08 


44.49 


43-34 


0.40 


0.31 


0.05 


0.04 


0.43 


0.41 


0.18 


0.31 


0.40 


0.30 


16 .45 


16.32 



Race. 



% 

37-5° 
0.52 
0.18 

44.12 
1.28 
0.11 
0.46 
0.22 
0.52 

15-09 



14 



MODUS OPERANDI 15 

From these analyses the constitutional of commercial 
bleach might be represented by the formula 

4CaOCl 2 -2Ca(OH) 2 -5H 2 

which assumes it to contain: 

68. o per cent of calcium hypochlorite, 
20.0 per cent of calcium hydroxide, 
and 1 2. o per cent of water. 

In this formula calcium hypochlorite has been written 
CaOCk, but this substance actually contains one atom of 
oxygen less than the true hypochlorite, which has the con- 
stitutional formula CIO — Ca — OC1. This difference led 
some of the earlier chemists to regard CaOCk as a mixture 
of equal molecules of calcium chloride and calcium hypo- 
chlorite (CaCl2+Ca(OCl)2 = 2CaOCl2), but it has been 
definitely established that no calcium chloride exists in the 
free state in dry commercial bleach. 

Since the very earliest days when the process of bleaching 
was investigated it was considered to be a process of oxida- 
tion and it is not surprising that Lavoisier and his pupils, 
who had noted the strong decolourising action of the gas dis- 
covered previously by Scheele, should regard it as a com- 
pound that contained oxygen. They were confirmed in 
this view by the fact that an aqueous solution of the gas 
slowly evolved oxygen when placed in bright sunlight, and 
lost its bleaching properties. Watt disproved this and 
showed that the evolution of oxygen was due to the action 
of the chlorine on water. 

Cl 2 +H 2 = 2HCl+0. 

The bleaching action was not due to the chlorine "per se" 
but to the nascent oxygen produced in the presence of mois- 
ture. Later, when bleach and other chlorine compounds 
came into use as deodourisers, their action was attributed 



16 CHLORINATION OF WATER 

to the oxygen produced and when their germicidal proper- 
ties became known it was natural to assume that the destruc- 
tion of bacteria was due to the same cause. Some of the 
earlier experimental work supported this view. Fischer 
and Proskauer 1 found that humidity played an important 
part in chlorine disinfection, probably because it favoured 
oxidation. In air saturated with moisture micro-organisms 
were killed by 0.3 per cent of chlorine in three hours but 
when the air was dry practically no action occurred. They 
concluded that chlorine was not directly toxic. Warouzoff, 
Winogradoff, and Kolessnikoff 2 were unable to confirm the 
results of Fischer and Proskauer and found that a mixture of 
chlorine gas and air killed tetanus spores in one minute. 

The nascent oxygen hypothesis was clearly and suc- 
cintly expressed by Prof. Leal during the hearing of the 
Boonton, N. J., case and the following abstracts have been 
taken from his evidence: 

" . . . That on the addition of bleach to water the 
loosely formed combination forming the bleach splits up 
into chloride of calcium and hypochlorite of calcium. The 
chloride of calcium being inert, the hypochlorite acted upon 
by the carbonic acid in the water either free or half bound, 
splits up into carbonate of calcium and hypochlorous acid. 
The hypochlorous acid in the presence of oxidisable matter 
gives off its oxygen; hydrochloric acid being left. The 
hydrochloric acid then drives off the weaker carbonic acid 
and unites with the calcium forming chloride of calcium. 

"That the process was wholly an oxidising one, the work 
being done entirely by the oxygen set free from the hypo- 
chlorous acids in the presence of oxidizable matter. . . . 

"We have used during our investigations, the term 
'potential oxygen' as expressing its factor of power. When 
set free, it is really nascent or atomic oxygen and is, in its 
most active state, entirely different from the oxygen normally 
in water. ..." 



MODUS OPERANDI 17 

The reactions suggested are expressed in the following 
equations: 

(i). 2CaOCl 2 = CaCl 2 +Ca(OCl) 2 

(ii). Ca(OCl) 2 +C0 2 +H 2 = CaC0 3 +2HC10 

(iii). 2HC10 = 2HCl+0 2 

(iv). CaC0 3 +2HCl = CaCl 2 +C0 2 +H 2 0. 

Phelps, during the hearing of this case, suggested that 
hypochlorites were directly toxic to micro-organisms but 
this view was not supported by any definite evidence and 
the nascent oxygen hypothesis met with almost universal 
acceptance. Investigations made by the author in 191 5, 
1916 and 1917 have produced data which cannot be ade- 
quately explained by the nascent oxygen hypothesis. 3 

The disinfecting action of bleach can be most con- 
veniently considered by regarding it as a heterogeneous mix- 
ture of the reactants and resultants of the reaction 

CaO+H 2 0-r-Cl 2 ^ CaOCl 2 +H 2 

which is in equilibrium for the temperature and pressure 
obtaining during the process of manufacture. Under suit- 
able physical conditions the chlorine content can be increased 
to 40-42 per cent but such a product is not so stable as those 
represented by the analyses on page 14 and which contain 
approximately 20 per cent of excess hydrate of lime. The 
stability of bleach depends upon this excess of base (Griffen 
and Hedallen 4 ) and although magnesia can be partially 
substituted for this excess of lime, a minimum of 5 per cent 
of free hydrate of lime is required to ensure stability. 

On dissolving bleach in water the first action is the 
decomposition of calcium oxychloride into an equal number 
of molecules of calcium hypochlorite and calcium chloride. 

2CaOCl 2 = Ca(OCl) 2 -r-CaCl 2 . 



18 CHLORINATION OF WATER 

In dilute solution these salts are dissociated and hydrolysis 
tends to occur in accordance with the equations 

2 Ca(OCl) 2 +4H 2 *± 2 Ca(OH) 2 +HOCl+HCl and 
CaCl 2 +2H 2 0<=± Ca(OH) 2 +2HCl. 

Calcium hydrate and hydrochloric acid are both practically 
completely dissociated, i.e. there is a large and equal quantity 
of H' and OH', and the product is much greater than K. w 
(ionic product of water), and hence there is a combination 
of these ions, leaving the solution neutral and no undis- 
sociated acid or base exists. This statement is only approxi- 
mately correct as hydrochloric acid is slightly more dis- 
sociated than calcium hydroxide (ratio 9 : 8) and the 
solution is consequently slightly acid, i.e. the H' concen- 
tration is greater than 1 X io -7 . 

Hypochlorous acid is only very slightly dissociated, 
especially in the presence of the OC1' ion due to the dis- 
sociation of the Ca(OCl) 2 , as compared with Ca(OH) 2 and 
hydrolysis of the Ca(OCl) 2 proceeds with increased dilution. 
The action is best represented by the equation 

2Ca(OCl) 2 + 2H 2 <=± CaCl 2 + Ca(OH) 2 + 2HOCl. 

The hydrolytic constant of hypochlorous acid has apparently 
not been determined but as the acid is weaker than carbonic 
acid, which has a hydrolytic constant of 1X10 -4 , the value 
is probably between iXio -3 and iXio~ 4 . From the 

formula- r- = k W v in which 1 mole of pure Ca(OCl) 2 

(i—x)v 

is dissolved in v litres, x is the fraction hydrolysed, and k W y 
is the hydrolytic constant, complete hydrolysis occurs 
(x=i) when v is not greater than 1X10 4 litres. This is 
equivalent to a concentration of not less than 7.1 p.p.m. 
of available chlorine. Solutions of pure hypochlorites are 
alkaline in reaction because of the excess of hydroxyl ions 
(minimum concentration iXio~ 4 ). In solutions of bleach 



MODUS OPERANDI 19 

the hydrolytic action is retarded by the OH' due to the free 
base, and accelerated by the excess of H' caused by the 
dissociation and partial hydrolysis of CaCk; the final 
result is determined by the relative proportions and the 
effect of the free base usually preponderates. The addition 
of any substance that reduces the OH' concentration enables 
hydrolysis to proceed to completion and affords a rational 
explanation of the fact that solutions of bleach, on dis- 
tillation with such weak acids as boric acid, yield a solution 
of hypochlorous acid. It also explains why the addition 
of an acid is necessary in Bunsen's method (vide p. 79) 
of analysing hypochlorite solutions. It has been stated 
that when hydrochloric acid is employed the increase in the 
oxidising power is due to the action of the acid upon calcium 
chloride but this never occurs under ordinary conditions ; weak 
acids such as carbonic or acetic will give practically the same 
result as hydrochloric acid in solutions of bleach of the strength 
used in water treatment. The slightly higher result obtained 
with strong acids is due to the decomposition of chlorates. 

The effect of dilution alone is shown by the data given 
below. A 2 per cent bleach solution, containing very little 
excess base, was diluted with distilled water and the various 
dilutions titrated with thiosulphate after the addition of 
potassium iodide. In one series the solutions were titrated 
directly, and after acidification in the other. The results* 
were as follows: 



HYDROLYSIS OF BLEACH 


SOLUTION 




Strength of Solution. Grams Bleach 




Direct Titration Xioo 




Per 100 c.cms. 




Acid Titraton 




2.0 




3°-8 




O. 2 




34-3 




0. 1 




41.8 




0.02 




67-5 




0.002 




100. 





* Corrected for the alkali produced by HCIO +2KI =KC1 +KOH +I 2 . 



20 CHLORINATION OF WATER 

Although every precaution was taken to exclude carbonic 
acid, a portion of the hydrolysis was probably due to this 
acid, which would remove calcium hydrate from the sphere 
of action and consequently alter the equilibrium. The 
above figures are only applicable to the particular sample 
used; other samples containing different excesses of base 
would yield different hydrolytic values. The results are in 
agreement with the hypothesis presented and confirm the 
theoretical deduction that very dilute bleach solutions are 
completely hydrolysed if no salts are present that will dis- 
sociate and increase the OH' concentration. Hydrolysis is 
reduced by caustic alkalies and alkaline carbonates, and 
increased by acids and acid carbonates that reduce the OH' 
concentration. 

The effect of chlorides is anomalous and no adequate 
explanation for their action can be given at present. The 
addition of small quantities of sodium chloride (o.i per cent) 
increases the hydrolysis of bleach solutions but much larger 
quantities tend to the opposite direction. 

The effect of these substances upon the velocity of the 
germicidal action of bleach solutions is in the same direction 
as the hydrolysing effect. 4 Sodium chloride in quantities 
up to 10 parts per million has a very limited effect but 
larger quantities (90 p. p.m.) increase the velocity of the 
reaction. Sodium chloride, in the absence of hypochlorites, 
was found to have no influence upon the viability of B. coli 
in water. 

In quantities up to approximately 5 p.p.m., sodium 
hydroxide has but little influence; 5-10 p.p.m. reduce the 
velocity to a marked degree, but when the quantity of caustic 
is still further increased the germicidal action of the alkali 
commences to be appreciable and may nullify the retarding 
action on the hypochlorite. Normal carbonates tend to 
reduce the velocity of the germicidal action and bicarbonates 
to increase it. 



MODUS OPERANDI 21 

Sulphuric acid, even in very small quantities. (5 p.p.m.), 
has a marked accelerating effect and the total effect pro- 
duced is much greater than can be accounted for by the 
germicidal activity of the acid alone. Weak acids such as 
carbonic acid and acetic acid are also effective accelerators. 
In one experiment a 0.01 per cent solution of bleach was 
found to be 40 per cent hydrolysed. By passing carbonic 
acid gas this was increased to 95 per cent and the velocity 
of the germicidal action of this solution was found to be 
approximately 100 per cent greater than that of the uncar- 
bonated one. Norton and Hsu 5 have shown that the 
germicidal activity of some disinfectants is a function of 
the hydrogen ion concentration, but this factor is insufficient 
to account for the effect of acids on bleach solutions. 

The effect of sodium chloride on the bacteriological 
results, like that on the hydrolytic constant, is anomalous. 
Similar effects have been observed on the addition of this 
salt to phenol and other disinfectants. The raison d'etre 
of the increased activity is obscure but it is possible that 
the salt renders the organisms more susceptible to the 
action of the germicide. 

Ammonia, though decreasing the hydrogen ion concen- 
tration of bleach and other hypochlorite solutions, markedly 
increases the velocity of the reaction; chlorinated derivatives 
of ammonia (chloramines), which have a specific germic'dal 
action, are formed. These will be discussed at length in 
Chapter IX, p. 115. 

Rideal 6 has shown that the addition of ammonia to 
sodium hypochlorite destroys the bleaching activity in 
acid solution. This has been found by the author to be 
also true for calcium hypochlorite (bleach). If the bleach- 
ing effect is due to oxidation, the oxidising power of hypo- 
chlorites must be considered to be destroyed by the addition 
of ammonia. The property of oxidising organic matter in 
water is also destroyed; this is well, illustrated in Table II 



22 



CHLORINATION OF WATER 



which shows the rate of absorption of chlorine and chlora- 
mine by the Ottawa River water. The water used in this 
experiment contained 40 p.p.m. of colour and absorbed 
9.5 p.p.m. of oxygen (30 mins. at ioo° C). 



TABLE II* 





Absorption of Availa 


ble Chlorine at 63° F. 


Minutes. 


Chlorine as Bleach. 


Chlorine as Chloramine. 


Nil. 


ro.oo 


9.98 


5 


6 


5° 


9 


98 


10 


5 


9i 


9 


90 


20 


5 


18 


9 


90 


40 


4 


47 


9 


84 


60 


3 


90 


9 


84 


80 


3 


65 


9 


84 


20 hours 






9 


68 



* Results are parts per million. 



From a consideration of these and other experiments 
made by the author in January, 191 6, it became apparent 
that the nascent oxygen hypothesis entirely failed to explain 
the results obtained, and that they must be attributed to a 
direct toxic action of the chlorine or chloramine. 

Dakin et al. 7 arrived at a similar conclusion from a con- 
sideration of the results obtained during the use of hypo- 
chlorite solutions in the treatment of wounds by Carrel's 
method of irrigation. They attributed the marked bene- 
ficial action to the formation of chloramines in situ by the 
action of hypochlorous acid upon amino acids and proteid 
bodies. Compound chloramines (chlorinated aminoben- 
zoic acids) were prepared in the laboratory and found to 
give excellent results in reducing wound infection. Later, 
other compounds were prepared for the purpose of sterilising 
small quantities of water for the use of mobile troops (see 
p. 128). 



MODUS OPERANDI 



23 



Rideal 6 was the first to note the strong germicidal power 
of chloramine and attributed the persistent germicidal 
activity of hypochlorites in sewage to the formation of 
chloramine and chloramine derivatives. 

Further evidence against the nascent oxygen theory of 
chlorine disinfection is to be found in the fact that such 
active oxidising agents as sodium, potassium, and hydrogen 
peroxides have a much lower germicidal activity than 
chlorine when compared on the basis of their oxygen equiva- 
lents. Table III shows chlorine to be approximately five 
times as active as potassium permanganate when compared 
on this basis. 



TABLE III.*- 



-COMPARISON OF BLEACH AND POTASSIUM 
PERMANGANATE 





Bleach 

Available Chlorine 

0.35 p.p.m. 


Potassium Permanganate. 


Contact Period. 


Oxygen Equivalent. Parts Per Million. 




0.08 


0. 133 


0.266 


0.400 


Nil 


140 
90 
68 
63 
50 


122 

115 

108 

95 


us 

100 

95 
80 




30 mins 




1 hour 


80 


1* hours 


75 
50 


4 hours 





* Results are B. coli per 10 c.cms. 



The germicidal activity of oxidising agents has been 
shown by Novey and others to be somewhat proportional 
to the energy liberated during the reaction but even when 
this factor is taken into consideration chlorine compounds 
are more active than other oxidising agents. Hypochlorous 
acid is far superior to hydrogen peroxide as a germicidal 
agent and is as active as ozone, which liberates a greater 
amount of energy. 



24 CHLORINATION OF WATER 

2HC10 = 2HCI+O2 + 18,770 calories 
2H202 = 2H20+ 02+46,1 20 calories 
203 = 302+60,000 calories. 

Again, solutions of chlorine gas and hypochlorites having 
the same oxidising activity, as determined by titration with 
thiosulphate after the addition of potassium iodide and 
acid. i.e. contain equal amounts of available chlorine, show 
approximately the same germicidal activity in water. On the 
addition of ammonia, the hypochlorite solutions retain their 
ability to liberate iodine from potassium iodide (Wagner 
test) but the property of oxidising such dyestuffs as indigo 
is destroyed and the germicidal activity is increased. Am- 
monia, when added to solutions of chlorine gas, diminishes 
the property of liberating iodine from potassium iodide, 
the bleaching effect on dyestuffs, and the germicidal action. 
It is often assumed that chlorine forms hypochlorous acid 
on solution in water Cl2+H20 = HC10+HCl but the results 
obtained on the addition of ammonia indicate that either 
very little hypochlorous acid is formed or that ammonia and 
hypochlorous acid do not form chloramine in the presence 
of hydrochloric acid. 

When chlorine gas was treated with a 0.5 per cent solu- 
tion of ammonia in the proportion of 1 molecule of chlorine 
to 1. 90-1. 95 molecules of ammonia, Noyes and Lyon 8 
found that nitrogen and nitrogen-trichloride were formed in 
equimolar quantities. 

i2NH3+6Cl2 = N2+NCl3+9NH 4 Cl. 

Bray and Dowell 9 showed that this reaction depended 
upon the hydrogen ion concentration and proceeded in 
accordance with the following equations: 

(i). Acid solution 4 NH3+3Cl2 = NCl3+3NH 4 Cl 
(ii). Alkaline solution 8NH 3 +3Cl2 = N2+6NH 4 Cl. 



MODUS OPERANDI 



25 



In (i) with a ratio of chlorine to ammonia of 3 : 1 by weight, 
one-half of the chlorine is lost as ammonium chloride and 
one-half forms nitrogen trichloride, concerning which com- 
paratively little is known; in (ii) the whole of the chlorine 
forms ammonium chloride, which has no germicidal value. 

The effect of ammonia on the germicidal action of a 
solution of chlorine gas is shown in the Table IV. 

TABLE IV.*— EFFECT OF AMMONIA ON CHLORINE GAS SOLUTION 

Conditions. Colour of water 40 p.p.m. Turbidity, 5 p.p.m. 



Contact Period. 



Available Chlorine 0.20 p.p.m., Ammonia. 
Parts Per Million. 



Nil. 



Nil 

10 mins . 

1 hour. 

4 hours . 
24 hours . 



130 

135 
130 
120 
120 



140 
130 
112 
145 



130 

128 
no 
160 



13s 

120 

105 

170 



* Results are B. coli per 10 c.cms. 

Even when the ratio of CI : NH3 was 4 : 1 by weight, 
practically the same as was used in the experiments of 
Noyes and Lyon, and Bray and Dowell, quoted above, the 
germicidal action was totally destroyed and the 24-hour 
results showed aftergrowths which were somewhat pro- 
portional to the amount of ammonia added. This was 
probably due to the formation of ammonium chloride, which 
provided additional nutriment for the organisms. 

It has often been assumed that hypochlorite solutions 
are decomposed on addition to water containing free or 
half -bound carbonic acid with the production of free chlorine, 
but no evidence has been adduced in support. Free chlorine 
can be separated from hypochlorous acid in aqueous solu- 
tion by extraction with carbon tetrachloride and when this 
solvent is shaken with a carbonated hypochlorite solution 
it is found that only traces of chlorine are removed. 



26 CHLORINATION OF WATER 

Hypochlorous acid reacts with hydrochloric acid with 
the evolution of free chlorine HC10+HCl = Cl2+H20 but 
in very dilute solution the amount of free chlorine formed is 
exceedingly minute. Jakowkin 10 has shown that this 
reaction does not proceed to completion and that the con- 
centration of free chlorine can be calculated from the equation 
HCIOXH" XCr = 32oCl2 in which the reactions are expressed 
in gram molecules per litre. The hydrogen ions and chlor- 
ions are obtained from the dissociation of carbonic acid 
(H 2 C0 3 ^H-+HC0 3 ) and chlorides (NaCl<=±Na'+Cl') and 
also by the dissociation of hydrochloric acid produced by the 
interaction of hypochlorous acid and organic matter. 
HC10 = 0+HC1^H+C1'. If the formula of Jakowkin 
can be correctly applied to solutions containing fractions of 
a part per million of hypochlorous acid the free chlorine 
liberated by the addition of i p.p.m. of bleach to a water 
low in chlorides would be of the order io~ 7 -io -8 p.p.m. 

Sodium hypochlorite is probably hydrolysed in dilute 
solution in a manner similar to that of bleach. 

2 NaOCl = NaCl+NaOH+HC10. 

For solutions containing equal amounts of available chlorine, 
electrolytic sodium hypochlorite is more dissociated than 
bleach because of the absence of an excess of base, and this, 
together with the presence of sodium chloride, accounts 
for the slightly higher germicidal velocity obtained. The 
experience of pulp mills, with bleach and electrolytic hypo- 
chlorites, confirms this: the latter is a much quicker bleach- 
ing agent than bleach and it is often so rapid as to make it 
desirable to reduce the velocity by the addition of soda ash. 
Regarding hypochlorite solutions a phenomenon of 
more scientific interest than of practical importance has 
been noted by Breteau 12 who found that alkaline solutions 
of sodium hypochlorite containing 0.94 per cent of available 
chlorine lost 3.6 per cent of their titer on dilution with 



MODUS OPERANDI 27 

80 volumes of water; also that this loss was increased by 
the addition of small quantities of salt (sodium chloride) 
and more so by carbonates and bicarbonates. The author 
has noted similar losses on diluting bleach solutions and 
that the loss increased on standing. The loss can be 
explained by the decomposition of hypochlorous acid, in the 
presence of light, into hydrochloric acid and oxygen. 
2HC10 = 2HCl+0 2 . 

Chlorine Water. When a solution of chlorine in water 
is used as a germicide the chemical reactions that occur 
differ materially from those of hypochlorite solutions. On 
solution in water, hydration or solvation probably takes 
place with the production of heat. Cl2-Aq. = 2,600 calories. 
Chlorine water is comparatively stable but decomposes 
under the influence of light in accordance with the equation 
Cl2+H20 = 2HCl+0; a similar reaction occurs in the 
presence of organic matter or any substance capable of 
oxidation. Chlorine water contains only minute traces of 
hypochlorous acid and there is no evidence that the endo- 
thermic reaction 

Cl 2 -Aq+H 2 0=HC10-Aq+HCl-Aq 

-2600-68,460= -29,930-39,315-1815 

occurs in a measurable degree. 

From thermochemical considerations hypochlorous acid 
and chlorine water should be about equally active as oxidis- 
ing agents. 

2HC10-Aq = 2HCl+0 2 + i8,77o calories 

2Cl2-Aq+2H20 = 2HCl+02 + i5,34o calories 

2C12- + Aq-f 2H2O =2HC1+ 02+20,540 calories 

When a solution of chlorine or hypochlorite is added to 
water as a germicidal agent, a variety of reactions occur the 
character of which is determined by the nature of the mineral 
and organic matter in the water and the type of chlorine 



28 CHLORINATION OF WATER 

compound added. The general reactions are of three types 
(i) oxidation of the organic matter, (2) direct chlorination 
of the organic matter, and (3) a bactericidal action. 

In the treatment of waters that contain appreciable 
amounts of organic matter almost all the chlorine is con- 
sumed in reaction (1) and even with filter effluents it is 
probably true that oxidation accounts for the greater por- 
tion of the chlorine consumed. The author has found that 
a dosage of 0.02 part per million of available chlorine was 
more effective in destroying B. coli in distilled water than 
0.40 p.p.m. in a water absorbing 9.5 p. p.m. of oxygen (30 
mins. at ioo° C). 

Reaction (1) can be adequately explained by the nascent 
oxygen hypothesis and it is this reaction that determines the 
dosage required for effective sterilisation. (See Chap. III.) 

Very little information is available regarding reaction 
(2) but there is little doubt that a direct chlorination of the 
organic matter does occur and it is more than probable that 
these chlorinated derivatives are largely responsible for the 
obnoxious tastes and odours produced in some waters. It 
has been suggested that these were due to the formation 
of chloramines. This view was formerly supported by the 
author but the chloramine treatment at Ottawa and other 
places has demonstrated the inadequacy of this explanation. 
It is true that the odour of chloramine is stronger and more 
pungent than that of chlorine, but chloramine in the Ottawa 
supply, even with doses as high as 0.5 part per million of 
available chlorine, has caused no complaints. 

The odour of some of the organo-chloro compounds is 
more penetrating and obnoxious than those of chlorine and 
chloramine, and it is quite possible that some of the higher 
homologues of chloramine are in this class. It should be 
noted, however, that some of the chloro-amido compounds 
prepared by Dakin are white, odourless, crystalline sub- 
stances. 



MODUS OPERANDI 29 

Practically nothing is known regarding the specific nature 
of the mechanism involved in reaction (3). The hypothesis 
that chlorine, and chlorine compounds, exert a direct toxic 
action on the micro-organisms marks an advance in the 
science of water treatment but does not indicate the physio- 
logical processes involved. Cross and Bevan n have shown 
that chloro-amines have a tendency to combine with nitro- 
genous molecules and to become fixed on cellulose; it is 
therefore possible that reaction is a cytolytic one in which 
the chlorine attacks and partially or wholly destroys the 
membranous envelope of the organisms. A portion of the 
chlorine or chlorine-compound may also penetrate the mem- 
brane and produce changes that result in the death of the 
organism. 



(9 
do; 
(11 
(12 



BIBLIOGRAPHY 

Fischer and Proskauer, Rev. d'Hyg., 1884, 6, 515. 

Warouzoff, Winogradoff, and Kolessnikoff. Russkaia medicina, 

1886, Nos. 3 and 32. 
Race. Jour. Amer. Water Works Assoc, 1918, 5, 63. 
Griffen and Hedallen. Jour. Soc. Chem. Ind., 191 5, 34, 530. 
Norton and Hsu. Jour. Inf. Dis., 1916, 18, 180. 
Rideal, S. Jour. Roy. San. Inst., 1910, 31, ^t,. 
Dakin, Cohen, Duafresne, and Kenyon. Proc. Roy. Soc, 1916, 

89B, 232. 
Noyes and Lyon. Jour. Amer. Chem. Soc, 1901, 23, 460. 
Bray and Dowell. Jour. Amer. Chem. Soc, 191 7, 39, 905. 
Jakowkin. Zeit. f. Phys. Chim., 1890, 19, 613. 
Cross. and Bevan. Jour. Soc. Chem. Ind., 1898, 28, 260. 
Breteau. Jour. Pharm. Chim., 1915, 12, 248. 



CHAPTER III 

DOSAGE 

The amount of chlorine required for efficient treatment 
is very largely determined by the amount required to satisfy 
the oxidisable matter present in the water. Many experi- 
menters have reported results that would indicate that 
appreciable concentrations of chlorine are required for 
bactericidal action but the details of the technique, as pub- 
lished, show that the effect of the organic matter added 
with the test organism was not thoroughly appreciated. 
One cubic centimetre of a culture in ordinary peptone water, 
added to one litre of water, would increase the organic 
content by approximately 10 parts per million, an amount 
that would absorb appreciable amounts of chlorine. 

Other conditions also make it very difficult to compare the 
results obtained in the past: one of these is the degree of 
purity set as the objective. German bacteriologists added 
enormous numbers of the test organism and endeavoured 
to obtain the complete removal of the organism from such 
quantities as one litre of water with a contact period often 
as short as 10 minutes. Nissen, 1 of the Hygienic Institute 
of Berlin, found that a i : 800 dilution of bleach (420 p.p.m. 
of chlorine) was required to destroy B. typhosus in one minute 
and a 1 : 1600 dilution (210 p.p.m. of chlorine) in 10 minutes. 
Delepine 2 obtained somewhat similar results by means 
of the thread method for testing disinfectants. Phelps, 3 
using gelatine plates for enumeration of the bacteria, obtained 
a 90 per cent reduction of B. typhosus in twenty minutes 

30 



DOSAGE 



31 



with 5 p.p.m. of available chlorine; over 99 per cent reduc- 
tion in one hour, and over 99.99 per cent reduction in 18 
hours. Wesbrook, Whittaker, and Mohler 4 tested bleach 
solutions with various strains of B. typhosus by means of 
the plate method and found that the most resistant one was 
reduced from 20,000 per c.cm. to sterility (in 1 c.cm.) by 
3 p.p.m. of available chlorine in fifty minutes and that the 
least resistant one only required 1.0 p.p.m. with a thirty 
minutes' contact. 

Lederer and Bachmann 5 have reported the following 
results : 

TABLE V 

Percentage Reduction, 15 Minutes' Contact 



Available 

Chlorine 

p.p.m. 



O.I 
0.2 
0.3 
0.5 

0.7 
1.0 
3° 
5° 
Original 
number 
of organ- 
isms per 
c.cm. 



Nature of Test Organism. 



B. 

cloacae. 



99.69 

99-75 
100.00 



160,000 



B. 

fascalis 
alkali- 
genes. 



99.98 

99-99 
100.00 



9,5oo 



B. 

para- 
typhosus. 



99-97 
100.00 



3,000 



Proteus 
mira- 
bilis. 



8,000 



B. 

enter- 
itidis. 



99-83 

99.98 

IOO.OO 



180,000 



B. 

lactis 
aero- 
genes. 



99.17 

99.98 

1 00 . 00 



180,000 



B. 

cholerce- 
suis. 



95 
100 



500 



With the exception of P. mirabilis, which forms endospores, 
all the organisms were killed (less than 1 per c.cm.) by 0.5 
p.p.m. of available chlorine in fifteen minutes. 

All these observers found that B. coli, the organism 
usually employed as an index of contamination, had approxi- 



32 CHLORINATION OF WATER 

mately the same degree of resistance to chlorine as B. typhosus, 
though Wesbrook et al. directed attention to the varying 
viability of organisms derived from different sources. 

These experiments merely indicate the dosage required 
for exceptional conditions such as it is inconceivable would 
ever occur in water-works practice. No information is 
available regarding the actual B. typhosus content of waters 
that have caused epidemics of typhoid fever, but for the pres- 
ent purpose it may be assumed that the extreme condition 
would be a pollution by fresh sewage giving a B. coli content 
of i ,000 per c.cm. or 200 times worse than the average con- 
dition that can be satisfactorily purified without ' over- 
loading a filter plant (500 B. coli per 100 c.cms.). Experi- 
ments made by the author indicate that a suspension of 
1,000 B. coli per c.cm. in water, in the absence of organic 
matter, can be reduced to a 2 B. coli per 100 c.cms. standard 
(the U. S. Treasury Standard) by 0.1 p.p.m. of available 
chlorine in ten minutes at 65 ° F. This experiment indicates 
the amount of chlorine that is required for the bactericidal 
action only, x such a dosage could never be used in practice 
to meet a pollution of this degree because of the accompany- 
ing organic matter. In actual practice the author has 
experienced the above condition but once, and on that 
occasion the B. coli were derived from soil washings and not 
from fresh sewage. 

The amount of chlorine required for germicidal action 
is small, and the main factors that determine the dosage 
necessary to obtain this action are (1) the content of readily 
oxidisable organic matter (2) the temperature of the water, 
(3) the method of application of the chlorine and (4) the 
contact period. 

Oxidisable Matter. The oxidisable matter may be divided 
into two classes (a) inorganic and (b) organic. The inor- 
ganic constituents naturally found in water, that are readily 
oxidisable, are ferrous salts (usually carbonates), nitrites. 



DOSAGE 



33 



and sulphuretted hydrogen, and these react quantitatively 
with chlorine until fully oxidised. The oxygen value of 
chlorine is approximately one-quarter (actually 16 : 71) 
the available chlorine content in accordance with the equation 



CI 



O 



+H20 = 2HC1+— . One part per million of available 
71 16 

chlorine will oxidise 1.58 p.p.m. of ferrous iron, 0.197 p.p.m. 
of nitrous nitrogen; and 0.479 P-P-ui. of sulphuretted 
hydrogen. 

The organic matter found in water may be derived from 
various substances such as urea, amido compounds, and cel- 
lulose ; humus bodies derived from soil washings and swamps 
may also be present. The humus compounds of swamps 
and muskeg are usually associated with the characteristic 
colour of the water derived from these sources. The effect 
of this coloured organic matter upon the chlorine dosage 
is well illustrated in Table VI. In this experiment B. coli 



TABLE VI.*— EFFECT OF COLOUR 
Temperature 63° F. 



Contact Period. 


Water "A" Colour 3 

Available Chlorine 

p.p.m. 


Water " B " Colour 40 

Available Chlorine 

p.p.m. 




0. 2 


0. 2 


0.4 


0.5 


Nil 


194 
121 

7 





194 

165 

95 

4 

1 



194 

129 

20 



1 




194 
66 


5 minutes 


1 hour 




5 hours 




24 hours 




48 hours 









* Results are B. coli per 10 c.cms. of water. 

was used as the test organism and the only varying factor 
was the organic matter. To obtain the same result with a 
contact period of one hour at 63 ° F. it was necessary to 
use about two and one-half times the amount of chlorine 



34 



CHLORINATION OF WATER 



with a water containing 40 p. p.m. of colour as with one 
practically free from colour. It will be noted that water 
"A," in which the colour had been reduced to 3 p.p.m. by 
coagulation with aluminium sulphate, required a greater 
dosage of chlorine than was necessary for bactericidal action 
only. This was due to a residual organic content which 
produced none or but a trace of colour, for although the col- 
our had been reduced by 92 per cent the organic matter, as 
measured by the oxygen absorbed test, had only been 
reduced by 70 per cent. 

The results obtained by Harrington 6 at Montreal are 
in the same direction. During the greater part of the year 
the water is obtained from the St. Lawrence river, which is 
colourless and low in organic matter; in the spring months 
the flood waters of the Ottawa, a highly coloured river, 
enter the intake and necessitated a much higher dosage. 



Chlorine Treatment at Montreal 






Source of Supply. 


Alkali- 
nity. 


Colour. 


Oxygen 
Absorbed 
(30 mins.) 


Chlorine 

Required 

p.p.m. 


Bacteria 
per c.cm. 


Per Cent 
Removed. 


Ottawa river 

St. Lawrence river . . 


15-20 
90-IOO 


50-70 

Nil. 


14.O 
O.30 


I.50 
O.30 


3,000 
500 


over 98 
over 99 



Ellms 7 obtained similar results and reported "that the 
rate at which sterilisation proceeds varies, in a general way, 
directly with the concentration of the applied available 
chlorine and the temperature, and inversely as the amount 
of easily oxidisable matter present." 

Experience with filter plants shows the same facts, the 
amount of chlorine required for the sterilisation of a filter 
effluent being invariably less than that necessary to purify 
the raw water to the same extent. 

The effect of coloured organic matter upon the absorp- 
tion of chlorine, in the form of hypochlorite, is shown on 
Diagram I. 



DOSAGE 



35 



The shape of the curve obtained with a colour of 40 p.p.m. 

somewhat resembled that of a mono-molecular reaction and 

the results were calculated accordingly. The mathematical 

dN 
expression of this law is — - = KN where N is the concentration 

of the available chlorine in parts per million. Integrating 

DIAGRAM I 

EFFECT OF COLOUR ON ABSORPTION OF CHLORINE BY WATER 



10 



9 9 



5 - 





^rColour^S 






Absorption of Chlorine 


Value of K calculated from 






by water at 63°F. 




Lo Slrr 

When t, 1*0 t2-tl 




Time of 

Contact 

in Minutes 


Colour of Water 


Time of 
Contact 
in Minutes. 


3 


25 


40 


Colour 


Nil 
5 


10.00 
9.62 








3 


25 


40 




7.70 


6.50 


s 


0.0033 


0.0227 


0.0374 






10 


9.41 


7.03 


5.91 


10 


0.0020 


0.0153 


0.0228 






20 


9.17 


6.10 


5.18 


20 


0.0018 


0.0096 


0.0190 






40 


8.95 


5.82 


4.17 


40 


0.0012 


0.0057 


0.00S7 






60 


8.85 


5.63 


3.90 


60 


0.0008 


0.0041 


0.0068 






SO 


8.80 


5.5S 


3.65 


80 


0.0007 


0.0032 


0.0056 






"■^^.^^r Colour = 25 






^^-^^Colour = 10 
1 1 1 





10 



20 40 

Time of Contact Minutes 



80 



between h and t 2 the formula K = 



log 



N 2 



h~h 



is obtained. If 



the compound absorbing the chlorine were simple in character, 
and the chlorine were present in large excess, the value of K 
would be constant. In the experiments recorded, K con- 
stantly decreases, due to the decreasing concentrations of 
the reacting substances and the complex nature of the organic 
matter. 



36 



CHLORINATION OF WATER 



The results show the effect of organic matter on the reduc- 
tion of the chlorine concentration available for germicidal 
action and also the importance of avoiding a local excess of 
chlorine (vide p. 41). 

An effort has been made by some observers to find a quan- 
titative relation between the organic matter, expressed as 
oxygen absorbed in parts per million, and the chlorine required 
for oxidation, but without definite result. Some of the results 
obtained are given in Table VII. 



TABLE VII.— OXYGEN TO CHLORINE RATIO 



Observer. 


n _ t _._ Oxygen Absorbed 
Chlorine Absorbed" 


Rouquette 


I 

Less than 1 

0.4 
0.4 
0. 22 


Bonjean 


Orticoni 


Valeski and Elmanovitsch 

Race 


Theoretical 





The value of 0.4 (0.39) obtained by the author is the average 
of over one hundred determinations covering a period of two 
years. The experiments of Zaleski and Elmanovitsch were 
made with the water of the Neva River. 

The divergence in the ratios affords additional evidence 
in favor of reaction (2) mentioned on page 28 and also shows 
that the chlorinated compounds are less readily oxidized than 
those from which they are produced. Heise 8 has found 
that the amount of chlorine consumed is usually proportional 
to the concentration in which it is added though not neces- 
sarily a function of the concentration of the organic matter. 

Temperature. The evidence regarding the effect of tem- 
perature upon the dosage required is somewhat conflicting. 
Ellms (vide supra) found that the velocity of the germicidal 
action varied directly with the temperature and this has also 



DOSAGE 



37 



been the author's experience with laboratory experiments. 
Typical examples of these are given in Tables VIII and IX. 

TABLE VIII.*— EFFECT OF TEMPERATURE 
Available Chlorine 0.4 Part Per Million 



Contact Period. 



Nil 

5 minutes. 
1 . 5 hours . 
4 . 5 hours . 
24 hours . . 
48 hours . , 



Temperature, degrees, Fahrenheit. 



36 



424 

320 

148 

38 

2 



70 



424 

280 

76 

14 



* Results are B. coli per 10 c.cms. 



98 



42* 
240 



TABLE IX.*— EFFECT OF TEMPERATURE 

Available Chlorine 0.2 Parts Per Million 



Contact Period. 



Temperature, degrees, Fahrenheit. 



36 



Nil 

5 minutes . 

1 hour. . . 

4 hours . . 

24 hours . . . 

48 hours . . , 

72 hours. . 

96 hours . . 

120 hours. . 



240 
240 
245 
21S 
143 
130 



240 
250 

23S 
190 
130 

59 

28 

16 

6 



240 
2 35 
195 
170 

ii5 
19 



* Results are B. coli per 10 c.cms. 

The reaction velocity of a germicide is proportional to the 
temperature 9 and the influence of temperature may be 

mathematically expressed by the formula — - = ^(7 , 2 — T\), in 

K2 

which K\ and K2 are the constants of the reaction at tempera- 



38 



CHLORINATION OF WATER 



tures T2 and T\ y respectively, and 6 is the temperature co- 
efficient. From the value of 8, the velocity constant of a 
germicide for any temperature may be calculated from the 
equation Kt = K2o°X Q {T ~ Tm \ K\ and K2 are obtained from 
Ni 



log 



the formula KT = 



N 2 



in which N1 — N2 is the number of 



h-h 

bacteria destroyed in the interval t2 — h 

A reduction of temperature also lowers the oxidizing 
activity of the chlorine so that a greater concentration is 
available for germicidal action. This is shown by the results 
plotted in Diagram II. 



DIAGRAM II 

EFFECT OF TEMPERATURE ON ABSORPTION OF CHLORINE BY WATER 



Absorption of Chlorine by water 
containing 40 p.p.m. of colour 



Value of K. calculated from 
absorption at 63T. 



Los -^ 




40 60 

Time of Contact Minutes 



Tables VIII and IX, however, show that the temperature 
coefficient of the germicidal action has a greater effect than 



DOSAGE 39 

the reduction in the amount of chlorine absorbed and removed 
from the reaction. 

The results obtained on the works scale with these waters 
are very different to the laboratory ones and show that more 
chlorine is required during the summer season than in winter. 
The results with bleach and liquid chlorine are in the same 
direction (vide Diagrams III and IV). The bleach was reg- 
ulated so as to maintain a constant purity, whilst in the other 
case the dosage was constant with a varying B. coll content. 
In Diagram IV the B coli is plotted ; this does not represent 
all the factors involved as the B. coli content of the treated 
water is also a function of that of the raw water, but in the 
example given this factor is of no moment because it was 
comparatively constant during the period plotted (extreme 
variation 80 per cent) . 

The discrepancies between the laboratory and works results 
cannot be easily explained. The only difference in the con- 
ditions is the nature of the containing vessel. Glass is prac- 
tically inert at all temperatures but the iron pipes, through 
which the water passed before the samples were taken, may 
exert an absorptive influence on the chlorine at the higher 
temperatures experienced during the summer months. 

Waters containing organic matter that differs much in 
quantity from the examples above may yield very different 
results and no generalisation can be made that will cover all 
cases. An increase of temperature increases the germicidal 
velocity and also the rate of absorption of chlorine by the 
organic matter; other factors determine which of these com- 
petitive actions predominates. 

Method of Application (admixture). A thorough admix- 
ture of the water and chlorine is a sine qua non for successful 
operation. This should, if possible, be attained by natural 
means, but if there is any doubt as to the efficiency of the mix- 
ing process, mechanical appliances should be utilised. Pumps, 
especially centrifugal pumps, constitute a very convenient 



40 



CHLORINATION OF WATER 



•jqcj 8,30(1 J8 1 C AV J° ajn^Bjsdraax 



o 

CO 


o o o o 
t- o 10 -gi 


8 












\s° ° 


^ 












i 
i 


fc 










,.-''''' 










,,,'-'' 






60 
>> 












| 








"""""-^^v 


^_ 






C 












HI 


. 


i-a 



su^o'd ooi jo< i hod *a; 

"jq'Gj s.Saa ja^EAV JO ajn;Ejaduiax 



o 


c 


D 


s 


o 




c 
































/// 


'" 














,~~ 


"""l 












_ 


.-'-" 


—— "* 








i a 
i b 







^' 














§ i 




\ 
\ 
\ 
























""•*-- 






















\ 




















^*~- 


"**—- 


~~\- 


















°>o-f 




















1/ 


















1 

1 
4 





















3 


o 

3 




1/] 


?•> 


« 


3 


-d 


►n 


01 




a 


D 


y. 




p, 



,6 



Homim jad B^jBd aj entaomo axqcijEAy 



DOSAGE 



41 



and efficacious method of mixing the germicide and the water, 
and the solutions should never be injected into the discharge 
pipes when it is possible to make connections with the suctions. 
Inefficient admixture leads to local concentration of the 
chlorine, a condition which (vide p. 35), results in a wastage 
of the disinfectant. Two practical examples of this effect 
may be cited. In one case the water was free from colour 
and contained very little organic matter. This water was 
chlorinated at one plant by allowing the bleach solution to 
drop into one vertical limb of a syphon approximately 6,000 
feet long, the other vertical limb being used as a suction well 
for the pumps which discharged into the distribution mains. 
At the other plant the bleach solution was injected into the 
discharge pipe of a reciprocating pump through a pipe per- 
forated with a number of small holes. The results for two 
typical months are given in Table X. 





TABLE 


X.— EFFECT OF 


EFFICIENT MIXING 






Available 
Chlorine 

Parts Per 
Million. 


Bacteria Per c.cm. 




Month. 


Raw- 
Water. 


Treated Water. 


Per 100 cans. 




A. 


B. 


A. 


B. 


A. 


B. 


July 

August. . . . 


0. 20 
0. 20 


0.25 
0. 27 


864 
1. 108 


27 
12 


93 
120 


<o. 2 

<0. 2 


8.5 

IO. 2 



A =efficient mixing. B = inefficient mixing. 

The results with the " B " plant were very irregular. 
The hypochlorite and water did not mix thoroughly and, as 
several suctions pipes were situated in the suction shaft, 
there was no subsequent admixture in the pumps; this also 
caused complaints regarding taste and odour but the com- 
plaints were localised, and not general as would result from 
an overdose of solution due to irregularities at the plant. 

The second example deals with a water containing 40-45 
p.p.m. of colour. This supply was taken from the river by 



42 



CHLORINATION OF WATER 



low-lift pumps and discharged into a header which was con- 
nected with the high-lift pumps by two intake pipes about 
5.000 feet in length. During 19 14 a baffled storage basin of 
two hours capacity was constructed and in June the hypo- 
chlorite was added at the inlet to this basin by means of a 
perforated pipe. The object was to increase the contact 
period prior to the delivery of the water into the header. 
The results for this month were as follows : 



Available Chlorine 1.88 Parts Per Million 





Bacteria Per c.cm. Agar. 


B. Coll. 




3 Days at 
20 C. 


1 day at 
37 C. 


Index 
Per c.cm. 




410 

49 
88.2 


104 
26 

75-o 




Treated water 


0.036 

87. 5 


Percentage purification 



During August the point of application of the hypochlorite 
was changed from the inlet of the basin to the suctions of the 
pumps and the solution proportioned to the amount of water 
pumped by the starch and iodide test. The average of the 
daily tests for this month were: 

Available Chlorine 1.55 Parts Per Million 



Raw water 

Treated water 

Percentage purification 



Bacteria Per c.cm. Agar. 



3 Days at 
20 C 



26 
91.9 



1 Day at 
37 C. 



B. Coli. 

Index 

Per c.cm. 



O.600 
O.OOS 
99.2 



Here again thorough admixture produced better results 
than inefficient admixture plus a longer contact period. 
Langer 10 has also noted the effect of local concentration and 
found that the disinfecting action is increased by adding the 



DOSAGE 43 

bleach solution in fractions, a cumulative effect replacing 
that of concentration. 

The importance of the admixture factor was not thor- 
oughly appreciated during the earlier periods of chlorination 
but later installations, and particularly the liquid chlorine 
ones, have been designed to take full advantage of it. 

The point of application in American water-works practice 
varies considerably (Longley 11 ). In 57 per cent of those 
cases in which it is employed as an adjunct to filtration, it is 
used in the final treatment; in 26 per cent it is used after 
coagulation or sedimentation and before nitration; in the 
remaining 17 per cent it is applied before coagulation and fil- 
tration. The report of the committee adds: " The data at 
hand do not give any reasons for the application before coag- 
ulation. In general, an effective disinfection may be secured 
with a smaller quantity of hypochlorite, if it is applied after 
rather than before filtration. It should be noted that the 
storage of chlorinated water in coagulating basins, and its 
passage through filters, tend to lessen tastes and odors con- 
tributed by the treatment and this fact may in some cases 
account for its use in this way." 

Contact Period. Other things being equal, the efficiency 
of the treatment will vary directly, within certain limits, 
with the contact period. When a chlorinated water has to 
be pumped to the distribution mains directly after treatment, 
the dosage must be high enough to secure the desired standard 
of purity within twenty to thirty minutes. The chlorine is 
sometimes not completely absorbed in this period and may 
cause complaints as to tastes and odours. The examples 
given above show that the lack of contact period can be 
largely compensated by ensuring proper admixture. Expe- 
rience has amply demonstrated that there is no necessity 
to use heroic doses for water that is delivered for consumption 
almost immediately after treatment, and that, with proper 
supervision, complaints can be almost entirely prevented. 



44 



CHLORINATION OF WATER 



The general effect of the effect of contact period is shown 
in Tables VIII and IX on page 37. Another example of a 
coloured water is given in Table XL whilst Table XII shows 
the results obtained with a colourless water. 

TABLE XI.*— EFFECT OF CONTACT PERIOD 



Contact Period. 


Chlorine, Parts Per Million. 


0.30 


0.40 


0.55 


1 . 21 


Nil 

1 minute 

10 minutes 

20 minutes 


3,800 
1,400 
720 
35 


120 

5 














* Results are B. coli per 10 c.cms. 

TABLE XIL— EFFECT OF CONTACT PERIOD 

Available Chlorine 0.27 Part Pes Million 







Sampling 


Point. 


Bacteria Per can. 


Average of series of 


5,000 ft 


from 


pumping station 


300 


samples 


6,000 " 
7,000 " 


tt 




it tt 
tt tt 


203 
103 




12,000 " 


11 




tt tt 


86 




14,000 " 


It 




a tt 


87 



Table XIII is taken from the work of Wesbrock et al. 4 

TABLE XIII.*— TREATMENT OF MISSISSIPPI RIVER WATER 
Aug. 8, 1910 



Available CI. 
P.p.m. 


Contact Period. (Temp. 22°-26° C). 


30 Mins. 


1 Hr. 
30 Mins. 


3 Hrs. 


6 Hrs. 
30 Mins. 


24 Hrs. 


O 
0-5 

I.O 

i-5 

2.0 
2.5 
3° 


230,000 

14,000 

20 

10 

7 

7 

6 


200,000 

7.400 

14 

6 

8 

14 
12 


160,000 

2.000 

170 

16 

IO 

30 

5 


150,000 

6,000 

450 

45 

97 

116 

12 


140,000 
1 1 ,000 
60,000 
70,000 
70,000 
65,000 
16,500 



* Results are bacteria per c.cm. 



DOSAGE 45 

In Tables VIII. IX, XI, and XII, the bacteria decreased 
constantly with increase of contact period, but the results in 
Table XIII show that no advantage was to be gained by- 
prolonging the contact beyond three hours; after this period 
the bacteria commenced to increase in number and when 
twenty-four hours had elapsed the number approached the 
original. This increase in the bacteria is technically known 
as " aftergrowth " and will be discussed more fully in Chap- 
ter IV. 

The replies to queries sent out by the Committee on Water 
Supplies of the American Public Health Association n indi- 
cate that the contact period after treatment varies consider- 
ably in American water- works practice. Forty per cent of 
the replies indicated no storage after treatment; 18 per cent 
less than one hour; 9 per cent from one to three hours; 5 
per cent three to twelve hours ; 1 1 per cent twelve to twenty- 
four hours, and 17 per cent a storage of more than twenty- 
four hours. 

Turbidity is usually considered to exert an effect upon 
the dosage required but no definite evidence has been adduced 
in support of this hypothesis. Turbidity is generally caused 
by the presence of very finely divided suspended matter, 
usually silt or clay, which is inert to hypochlorites. The con- 
dition that produces turbidity, however, produces a concom- 
itant increase in the pollution and some of the organisms are 
embedded in mineral or organic material that prevents access 
of the chlorine to the organisms which consequently survive 
treatment. A larger concentration is required to meet these 
conditions but it is not necessitated by the turbidity per se. 

Effect of Light. Light exerts a marked photo-chemical 
effect on the germicidal velocity of chlorine and hypochlorites. 
When chlorinated water is passed through closed conduits 
and basins the effect of light is of course nil but in open con- 
duits and reservoirs this factor is appreciable and reduces 
the necessary contact period. The effect of light on labora- 



46 



CHLORINATION OF WATER 



tory experiments made with colourless glass bottles is so 
marked as to make it impossible to compare the results 
obtained on different days under different actinic conditions. 
The following figures illustrate the effect of sunlight: 



EFFECT OF SUNLIGHT 



Available Chlorine 0.35 p.p.m. 



Contact Period 




Determination of Dosage Required. The dosage required 
for the treatment of a water can only be accurately deter- 
mined by treating samples with various amounts of chlorine 
and estimating the number of bacteria and B. coli after an 
interval of time equal to that available in practice. The 
temperature of the water during the experiment should be 
the same as that of the water at the time of sampling. 

In order to limit the range covered by the experiments the 
approximate dosage can be ascertained from Diagram V if the 
amount of oxygen absorbed by the water is known. This 
diagram is calculated on the amount of available chlorine, 
present as chlorine or hypochlorite, that will reduce the 
B. coli content to the U. S. Treasury standard (2 B. coli per 
100 c.cms.) in two hours. If the oxygen absorbed values are 
determined by the four-hour test at 27 C. they should be 
multiplied by two. 

Another method which has been generally adopted for 
military work during the war, consists in the addition of 
definite volumes of a standard chlorine solution to several 
samples of the water and, after a definite interval, testing 



DOSAGE 



47 



for the presence of free chlorine by the starch-iodide reaction. 
The details of the method of Gascard and Laroche, which 
is used by the French sanitary service, have been given by 
Comte. 12 One hundred c.cms. of the water to be examined 
are placed in each of 5 vessels and 1, 2, 3, 4, and 5 drops of 
dilute Eau de Javelle (1 : 100) are added and the contents 
stirred. After twenty minutes, 1 c.cm. of potassium iodide- 
starch reagent (1 gram each of starch, potassium, iodide and 



DIAGRAM V 

RELATION OF DOSAGE TO OXYGEN ABSORBED 



1.U 

0.9 

a 

3 0.8 

s 

6 0.7 

a 
t0.6 

d 
Ck 

£0.5 


a 

| 0.4 

fo.3 

S 

|0.2 
> 
< 
0.1 































































































































































































































1.0 



2.0 



3.0 4.0 5.0 6.0 7.0 8.0 
Oxygen absorbed in 80 minutes at 100°C. 



9.0 10.0 11.0 



crystallized sodium carbonate to ioo c.cms.) is added and the 
samples again stirred. The lowest dilution showing a definite 
blue colour is regarded as the dose required, and the number 
of drops is identical with that required of the undiluted Eau 
de Javelle for 10 litres of water when the same dropping 
instrument is used. The actual concentration represented 
by these dilutions depends necessarily upon the size of the 
drops and the strength of the undiluted Eau de Javelle, 
but one drop per ioo c.cms. usually represents approximately 
i p.p.m. 



48 



CHLORINATION OF WATER 



In Horrock's method, as used in the British army, a 
standard bleach solution is added and is almost immediately 
followed by the zinc iodide-starch reagent. The two methods 
were compared by Massy, 13 who found that the French 
method gave an average result of only 0.06 m.gr. per litre 
(0.06 p.p.m.) higher than the English method. Water in the 
Gallipoli campaign required from 0.21 to 1.06 p.p.m. as 
determined by both methods. 

Dienert, Director of the Paris Service for investigating 
drinking water, adds 3 p.p.m. of available chlorine and 
allows the mixture to stand fifteen minutes after shaking; 
the residual chlorine is then titrated with thiosulphate. The 
amount absorbed is increased by 0.5 p.p.m. and in the 
opinion of Dienert this dosage is correct for a contact period 
of three hours. 

For military camps where a standpipe usually provides a 
reasonable contact period, it has been found good practice 
to add sufficient chlorine to give a rich blue colour with the 
starch-iodide reagent and subsequently reduce the dosage 
gradually until the water, after standing one hour, gives 
but a faint reaction to the test reagent. This method should 
be checked up as soon as possible by bacteriological examina- 
tions. An example of this method is given in Table XIV. 



TABLE XIV— CONTROL OF DOSAGE BY STARCH-IODIDE 
REACTION 



Starch-iodide 

Reaction After One 

Hour. 


Bacteria on Agar Per c.cm. 


B. Coli Per 


1 Day at 37 C 


2 Days at 20 C. 


100 c.cms. 


OOO©© 


40 


IS 


O 


OOOO© 


37 


18 


8 


OOOOO 


68 


268 


34 


OOOOO 


US 


553 


61 


Raw water 


"4 


685 


8 9 



The number of © signs indicates the intensity of the reaction. 



DOSAGE 49 



BIBLIOGRAPHY 

(i) Nissen. Zeit. f. Hyg., 1890, 8, 62. 

(2) Delepine, J. Soc Chem. Ind., 191 1, 29, 1350. 

(3) Phelps. Water Supply Paper No. 220, U. S. Geo. Survey. 

(4) Wesbrook, Whittaker, and Mohler, J. Amer. Public Health Assoc, 

1911, 1, 123. 

(5) Lederer and Bachmann. Eng. Rec, 191 2, 65, 360. 

(6) Harrington. J. Amer. Waterworks Assoc, 1914, 1, 438. 

(7) Ellms. Eng. Rec, 1911, 63, 472. 

(8) Heisse. Philippine Jour. Sci., 1917, 12, A, 17-34. 

(9) Norton and Hsu, Jour. Inf. Dis., 1916, 18, 180. 
(10) Langer. Zeit. f. Hyg., 1916, 81, 296. 

(n) Longley. J. Amer. Public Health Assoc, 1915, 5, 920. 

(12) Comte. J. Pharm. Chim., 1916, 14, 261. 

(13) Massy. J. Pharm. Chim., 1917, 15, 209. 



CHAPTER IV 
BACTERIA SURVIVING CHLORINATION 

A disinfectant is usually described as a substance capa- 
ble of destroying bacteria and other micro-organisms, and 
an antiseptic as one that restrains or retards their growth 
or reproduction. This distinction is entirely arbitrary as the 
ability of a substance to kill organisms or merely inhibit 
their growth depends upon the concentration employed. 

Chlorine and hypochlorites, even in minute doses, exert 
a toxic effect that is sufficient to produce death in organisms 
but when still smaller concentrations are employed the toxic 
effect is transient and the reproductive faculty may be 
entirely regained. 

The enumeration of bacteria by means of solid media 
depends upon the ability of the organism to reproduce at 
such a rate as to produce a visible colony within the period 
of incubation and any substance that prevents the growth 
of a visible colony is classified as a disinfectant; if on further 
incubation the bacterial count approximates that of the 
untreated sample the added substance has acted mainly as 
an antiseptic. In practice no substance acts entirely as an 
antiseptic as the organisms present have varying degrees of 
resistance and the less viable ones are killed by doses that 
are only antiseptic to the more resistant ones. An example 
of an astiseptic effect followed by a mild disinfectant action, 
caused by small doses of bleach is shown in Table XV. In 
this experiment the water disignated as control was from the 
same source as the treated water. In order to make the 

50 



BACTERIA SURVIVING CHLORINATION 



51 





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52 



CHLORINATION OF WATER 



bacterial count in this water approximately the same as in the 
treated water, the original count was reduced by diluting 
the sample with water from the same source, sterilised by 
boiling, and afterwards reaerated with sterile air. 

Table XVI shows the effect of a concentration of i.o 
p.p.m. of chlorine; the hypochlorite at this concentration 
acted almost entirely as a germicide or disinfectant. 

TABLE XVI.*— EFFECT OF CHLORINE AS A DISINFECTANT 

Available Chlorine i.o p.p.m. 



Plated. 




Incubation Period 


Days. 




Time. 


Day. 


2 


3 


4 


5 


6 


ii a.m 


I 
I 
I 
I 
2 

3 

4 
5 


2 

I 

O 

I 
O 

o 

5 

79 

915 


5 
1 

2 



13 

166 

1,410 


7 
2 

2 


16 

1,680 


8 
2 
2 
6 

1 

2,150 




1 2 noon 

2 p.m 


4 


4 p.m 


6 


io a.m 




io a.m 




io a.m 




io a.m 




Untreated water. . . . 


3,200 



* Results are bacteria per c.cm. 

Table XV shows a recovery of the anabolic functions 
after treatment with 0.1 p.p.m. of chlorine but since this was 
obtained by plating on such a suitable medium as nutrient 
gelatine, it is probable that reproduction in water having a 
low organic content would be still further diminished. This 
is indicated by the results obtained. 

There is no evidence of any marked difference in the 
resistance of ordinary water bacteria to chlorine and these 
are the first to be affected by the added germicide. The 
common intestinal organisms are also very susceptible to 
destruction by chlorine and there is considerable evidence 
that B. Coli is slightly more susceptible than many of the 
vegetative forms usually found in water. The specific 



BACTERIA SURVIVING CHLORINATION 53 

organisms causing the water-borne diseases, typhoid fever 
and cholera, are, on the average, not more resistant than 
B. coli. 

The spore-forming bacteria usually found in water are 
those of the subtilis group, derived largely from soil washings, 
and B. enteritidis sporogenes, from sewage and manure. The 
spores of these organisms are very resistant and survive all 
ordinary concentrations. Wesbrook et al. 1 found that 
3 p.p.m. of available chlorine had little effect on a spore- 
forming bacillus isolated from the Mississippi water and the 
author has obtained similar results with B. subtilis. 

Thomas, 2 during the chlorination of the Bethlehem, Pa., 
supply, found four organisms that survived a concentration 
of 2 p.p.m. of available chlorine: Bad. (BropJiilum, B. cuti- 
cularis, and B. subtilis, all spore formers and M. agilis. 

In practice no attempt is made, except in special cases, 
to destroy the spore-bearing organisms as they have no sani- 
tary significance and the concentration of chlorine required 
for their destruction would cause complaints as to tastes 
and odours if the excess of chlorine were not removed. Such 
doses are unnecessary and result in waste of material. It 
is found that, when the dose is sufficient to eliminate the 
B. coli group from 25-50 c.cms. of water, the majority of 
the residual bacteria are of the spore-bearing type. Smeeton 3 
has investigated the bacteria surviving in the Croton supply 
of New York City after treatment with 0.5 p.p.m. of available 
chlorine as bleach. Table XVII gives the results obtained. 

The organisms of the B. subtilis group outnumbered all 
the others, 66 (62.8 per cent) belonging to this group alone. 
This group contained B. subtilis — Cohn (36 strains), B. 
tumescens — Chester (15 strains) B. ruminatus — Chester (13 
strains), and B. simplex— Chester 1904, (2 strains). Three 
of the four coccus forms were classified as M. luteus. No 
intestinal forms were found. 

Clark and De Gage 4 in 1910 directed attention to the 



54 



CHLORINATION OF WATER 



fact that the bacterial counts, made at 37 C. on chlorinated 
samples, were often much greater than the counts obtained 
at room temperature. "This phenomenon of reversed ratios 
between counts at the two temperatures," they stated, "has 
been occasionally observed with natural water, but a study 
of the record of many thousands of samples shows that the 
percentage of such samples is very small, not over 3-5 per 
cent. . . . On the other hand 20-25 per cent, of samples 

TABLE XVII.— ORGANISMS SURVIVING TREATMENT 
NEW YORK 

(Smeeton) 





Morphology 


Spore 
Formation 


Gelatine 
Liquefaction 


Reaction in 
Litmus Milk 




Bacilli. 


Cocci. 


Pos. 


Neg. 


Pos. 


Neg. 


Pos. 


Neg. 


No. of strains 

Per cent 


IOO 
95-2 


5 
4-7 


89 
84.7 


16 
15-2 


68 
64.7 


37 
35-2 


98 
93-3 


7 
6 6 







Indol 
Production 



Pos. 



Neg. 



Acid 
Production 
in Glucose 



Pos. 



Neg. 



Reduction 
of 

Nitrates 



Pos. 



Neg. 



Inhibition by 
Gention 
Violet 



Neg. 



No. of strains. 
Per cent 



75 
7i-4 



30 

28.5 



61 
58 



44 
41.9 



40 
38 



65 
61 .9 



93-3 



7 
6.6 



treated with calcium hypochlorite show higher counts at 
body temperature than at room temperature." Clark and 
De Gage were unable to state the true significance of this 
phenomenon but were of the opinion that it was not due to 
larger percentages of spore-forming bacteria in the treated 
samples. Other observers, on the contrary, have invariably 
found the spore-formers to be more resistant to chlorine 
and thcrmophylic in type. 

The removal of intestinal forms is, of course, merely a 
relative one and when large quantities of treated water are 
tested their presence can be detected. 



BACTERIA SURVIVING CHLORINATION 55 

The author, in 1915, made a number of experiments to 
ascertain whether the B. colt found after chlorination were 
more resistant to chlorine than the original culture. The 
strains surviving treatment with comparatively large doses 
were fished into lactose broth and subjected to a second 
treatment, the process being repeated several times. The 
velocity of the germicidal reaction with the strains varied 
somewhat, but not always in the same direction, and the 
variations were not greater than were found in control experi- 
ments on the original culture No evidence was obtained 
that the surviving strains were in any way more resistant to 
chlorine than the original strain; in considering the results it 
should be borne in mind that the surviving strains were 
cultivated twice on media free from chlorine before again 
being subjected to chlorination. 

A number of the strains that survived several treatments 
were cultivated in lactose broth and the acidity determined 
quantitatively. All the cultures produced less acid that the 
original culture, and the average was materially less than the 
original. These results point to a diminution of the bio- 
chemical activity by action of the chlorine. 

A point of perhaps more scientific interest than practical 
utility is the relative proportion of the various types of B. coli 
found before and after treatment with chlorine The author, 
in 1914, commenced the differentiation of the types by means 
of dulcite and saccharose and obtained the results shown in 
Table XVIII. These figures are calculated from several 
hundreds of strains. 

Although there is a slight difference in the relative propor- 
tions of the types found at Ottawa and Baltimore, both 
sets of results show definitely that there is no difference in the 
resistance of the various types to chlorination. 

Aftergrowths. In Tables XIII (p. 44) and XV (p. 51), 
it will be noticed that, after the preliminary germicidal 
action has subsided, a second phase occurs in which there is 



56 



CHLORINATION OF WATER 



a rapid growth of organisms. This is usually known as after- 
growth. When the contact period between chlorination and 
consumption is short, the reaction does not proceed beyond 
the first phase, but when the treated water is stored in service 
reservoirs the second phase may ensue. At one purification 
plant, where the service reservoirs are of large capacity, 
the aftergrowths amounted to 20,000 bacteria per c.cm. 
although the water left the purification plant with a bacterial 
count usually lower than 50 per c.cm. 

TABLE XVIII.— TYPES OF B. COLI SURVIVING CHLORINATION 









Percentage 


of Organisms. 








B. coli 
communis 


B. coli 
communior 


B. lactis 
aerogenes 


B. acidi 
lactici 




Raw. 


Chlori- 
nated. 


Raw. 


Chlori- 
nated. 


Raw. 


Chlori- 
nated. 


Raw. 


Chlori- 
nated. 


Ottawa, 1914 

Ottawa, 1915 

Baltimore, 1913 *.. 


5 

8 

II 


4 
8 

14 


40 
5° 
33 


48 
46 
25 


44 
34 
35 


36 
31 
31 


II 

8 

21 


12 
15 
30 



* Thomas and Sandman. 5 



Regarding the nature of this aftergrowth, there has been 
a considerable difference of opinion: some regard it as the 
result of the multiplication of a resistant minority of practi- 
cally all the species of organisms present in the untreated 
water; others, that it is partially due to the organisms being 
merely " slugged" or " doped," i.e. are in a state of suspended 
animation, and afterwards resume their anabolic functions; 
whilst others believe that with the correct dosage of chlorine, 
only spore-forming organisms escape destruction and that 
the aftergrowth is the result of these cells again becoming 
vegetative. 

The aftergrowths obtained under the usual working con- 
ditions vary according to the dosage of chlorine employed, 
and none of the above hypotheses alone provides, an adequate 



BACTERIA SURVIVING CHLORINATION 57 

explanation. When the dosage is small, a small number of 
active organisms, in addition to the spore bearers, will escape 
destruction, and others will suffer a reduction of reproductive 
capacity. The flora of the aftergrowth in this case will only 
differ from the original flora by the elimination of a majority 
of the organisms that are most susceptible to the action of 
chlorine and the weaker members of other species of greater 
average resistance. As the dose is increased these factors 
become relatively less important until a stage is reached 
when only the most resistant cells, the spores, remain. The 
resultant aftergrowth must necessarily be almost entirely 
composed of spore-bearing organisms. A small number of 
the most resistant members of non-sporulating organisms 
may also be present but they will, in the majority of instances, 
form a very small minority. This is the condition that 
usually obtains in practice and it is necessary to consider 
whether the aftergrowth may have any sanitary significance. 

Concerning the secondary development of B. coli, the usual 
index of pollution, there is but little information. H. E. 
Jordon 6 reported that, of 201 samples, 21 gave a positive 
B. coli reaction immediately after treatment, 39 after stand- 
ing for twenty-four hours, and 42 after forty-eight hours. 
These increases were confined to the warm months, the cold 
months actually showing a decrease. The following figures, 
taken from the author's routine tests for 1913 and 1914, 
show a similar tendency, but an analysis of the results by 
months did not show that this was confined to the warm 
season. The sequence of the results from left to right, in 
the following Table, is in the same order as the contact 
period. Approximately 290 samples were taken at each 
sampling point. 

At station No. 2 the germicidal action was still proceed- 
ing but at No. 5, representing an outlying section of thp 
city, the increase in the B. coli content is very apparent. 

During 191 5 and 1916 the author endeavoured to duplicate 



58 



CHLORINATION OF WATER 



these results under laboratory conditions and entirely failed. 
These experiments, which were made with the same materials 
as were in use at the city chlorination plant, but in glass con- 
tainers, were usually only carried to a forty-eight hours con- 
tact, as this was the extreme limit for the city mains; one, 
however, was prolonged to rive days. Many experiments 
were made, under varying conditions, with similar results. 
Typical examples are given in Tables VI. VIII and IX on 
pages 33 and 37. 

TABLE XIX.— AFTERGROWTHS OF B. COLI 

Percentage of Samples Showing B. Coli in 10 c.cms. 



1913- 
1914. 





Sampling Po 


INT No. 




I 


2 


3 


4 


5 


15-2 

7.0 


14.4 

5-7 


16.3 
6.0 


16.8 


26.8 
11. 6 



In every case there was persistent diminution in the 
number of B. coli with increase of contact period. Deter- 
mination of the bacterial count on nutrient agar showed 
that, in several experiments, the aftergrowth had commenced, 
and in some instances there was evidence that the second cycle 
was partially complete i.e. the number had reached a maximum 
and then commenced to decline. The time required for the 
completion of the two cycles, comprising the first reduction 
caused by the chlorine / the increase or aftergrowth, and the 
final reduction due to lack of suitable food material, is 
dependent upon several factors of which the dosage and 
temperature are the most important. With a small dosage 
the germicidal period is short and the second phase is quickly 
reached; with large doses, the second phase is not reached 
in forty-eight hours; the higher the temperature the quicker 
is the action and the development of the aftergrowth. These 
statements refer only to the bacteria capable of development 



BACTERIA SURVIVING CHLORINATION 59 

on nutrient agar. The B. coli group behaved differently 
and persistently diminished in every case. If B. typhosus 
acts in a similar manner to B. coli, the laboratory experiments 
show that aftergrowths are of no sanitary significance and 
can safely be ignored, but as the results obtained in practice 
are contradictory to the laboratory ones, the matter must be 
regarded as sub judice until more definite evidence is available. 

It is common knowledge that samples of water from 
"dead ends" of distribution mains show high counts and 
much larger quantities of B. coli than the water delivered 
to the mains. This is another phase of aftergrowth problem 
that often causes complaints and can only be eliminated by 
" blowing off " the mains frequently or by providing circulation 
by connecting up the " dead ends." One extreme case of 
this description might be cited. A small service was taken 
off the main at the extreme edge of the city to supply a 
Musketry School two miles away and was only in use for a 
few months in the summer season. This service pipe delivered 
water containing B. coli in a considerable percentage of the 
10 c.cm. samples and in a few instances in i c.cm., although 
the water delivered to the city mains never exceeded 2 B. coli 
per 100 c.cms. and averaged about one-tenth that quantity. 
No epidemiological records of the effect of this water are 
available because it was put through a Forbes steriliser before 
consumption. 

In some instances the rate of development of the organisms 
after chlorination is greater than in the same water stored 
under similar conditions. This is especially noticeable in 
the presence of organic matter and has been ascribed to the 
action of the chlorine on the organic matter with the pro- 
duction of other compounds that are available as food material 
for the organisms. 

Houston, during the treatment of prefiltered water Lin- 
coln in 1905, found that although the removal of B. coli 
and other organisms growing at 37 ° C. was satisfactory, 



60 



CHLORINATION OF WATER 



there was almost invariably an increase in the bacteria 
growing on gelatine at 20 ° C. This was ascribed to the action 
mentioned above and the chemical results supported this view, 
more organic matter being found in the filter effluents 
than in the prefiltered water. Rideal's experiments with 
sewage at Guildford indicate that a similar action may occur 
in contact beds. The addition of bleach to the prefiltered 
water at Yonkers also resulted in an increased count and in 
these instances the aftergrowths are due to a disturbance 
of the equilibrium by the action of the chlorine on the zooglea 
and other organic matter invariably found in ripe filters. 
Similar results can be produced by the addition of chlorinated 
water to small experimental sand filters. This is shown by the 
results in Tables XX and XXI. 

TABLE XX.— AFTERGROWTHS IN SAND 



Available 


Bacteria Per 
Gram of 
Sand After 


Typical B. coli After 
24 Hours. 


Free chlorine 
After 24 Hrs. 


Chlorine in 
Water p. p.m. 


Without 
Acidifi- 
cation. 


After 


3Hrs. 


24 Hrs. 


100 Gr. 


10 Gr. 


1 Gr. 


0.1 Gr. 


Acidifi- 
cation. 


Nil 

3-o 

5° 

7-o 

10. 


12,000 
80 
So 
25 
26 


21,000 
114,000 
150,000 
214,000 
500,000 


+ 


+ 


+ 


- 


- 


— 



TABLE XXL— AFTERGROWTHS IN SAND 





Eacteria Per Gram of Sand After 


in Water p. p.m. 


3 Hours. 


24 Hours. 


48 Hours. 


Nil 

0.1 

0-3 

o'-S 

1.0 


70,000 
7,200 
5,240 
5,120 
1,100 


20,400 
6,400 
4,700 
8,800 


I2,8oo 
II,200 
10,800 
20,400 



BACTERIA SURVIVING CHLORINATION 61 

It is observable that the effect of small doses was com- 
paratively small and transient; large doses of bleach reduced 
the bacteria very materially but the reduction was not main- 
tained and the subsequent increase was abnormally rapid. 

BIBLIOGRAPHY 

(i) Wesbrook, Whittaker and Mohler. J. Amer. Pub. Health Assoc, 
ion, i, 123. 

(2) Thomas. Jour. Ind. and Eng. Chem., 19 14, 6, 548. 

(3) Smeeton. Jour, of Bact., 191 7, 2, 358. 

(4) Clark and De Gage. Rpt. Mass. B. of H, 1910, p. 319. 

(5) Thomas and Sandman. J. Ind. and Eng. Chem., 1914, 6, 638. 

(6) Jordan, H. E. Eng. Record, 1915, May 17. 



CHAPTER V 

COMPLAINTS 

The complaints that have been made against chlorinated 
water since the practice was commenced have been very 
diversified in character and can be numbered by the legion 
and although some have been justifiable, the great majority 
has been unsubstantiated and must be ascribed to auto- 
suggestion. 

Almost every one who has had charge of chlorination 
plants has noted the latter phenomenon, for in some instances 
complaints have been made following the publication of 
the information that chlorination was to be commenced but 
antecedent to its actual operation, and in others when for 
some reason or another, the chlorination plant has been 
temporarily stopped. Similar observations have been made 
in laboratory experiments when independent observers have 
been requested to detect the chlorinated waters from an equal 
number of treated and untreated waters. Such observers 
are wrong in the majority of the waters which they designate 
as treated ones if the dosage is not in excess of that required 
for satisfactory purification. 

One amusing example of auto-suggestion was experienced 
by the author some years ago. During a ceremonial visit to 
the waterworks, the Mayor and several civic representatives 
happened to visit a hypochlorite plant that was built on a 
pier over the river and which had no ostensible connection 
with the city mains. One of the party expressed a desire 
for a drink of good river water without any hypochlorite 

62 



COMPLAINTS 63 

in it and was served with water from the plant supply by an 
assistant engineer of the waterworks department. The 
water was consumed by all with great relish and as it was 
being finished, the writer entered the plant and was invited 
to join them in the enioyment of this "dopeless" water; 
on asking where it had been obtained he was astonished to 
hear that it was from a tap which was supplied with the 
ordinary chlorinated water of the city. 

On many occasions, complaints are justifiable and should 
be carefully investigated instead of, as is often the case, 
being attributed to auto-suggestion. The time and energy 
that are often devoted to endeavouring to persuade water 
consumers that their complaints are without foundation, 
can better be utilised in so improving the chlorination proc- 
ess as to eliminate tastes and odours. All complaints should 
be carefully investigated and a record kept for future reference, 
for the cause, although not manifest at the time, may be dis- 
covered later. The records then provide valuable corrob- 
orative evidence. 

The nature of the complaints against chlorinated water 
is very diversified and includes imparting foreign tastes 
and odours, causing colic, killing fish and birds, the extraction 
of abnormal amounts of tannin from tea. the destruction of 
plants and flowers, the corrosion of water pipes, and that 
horses and other animals refuse to drink it. 

Tastes and Odours. When an excess of hypochlorite or 
liquid chlorine is added to a water it imparts a sharp pungent 
odour and acid taste, characteristic of chlorine, that render 
it offensive to the nose and palate. In some instances the 
presence of chlorine compounds is not obtrusive when the 
temperature of the water is low but becomes so when the 
temperature is raised. It is especially observable when 
the faucets of hot water services are first opened and the 
chlorine is carried off as a vapour by the other gases liberated 
by the reduction in pressure. For this reason the complaints 



64 CHLORINATION OF WATER 

regarding hot water are relatively more numerous and some- 
times constitute the whole of the complaints. In cold water 
containing appreciable quantities of mineral salts the hypo- 
chlorites and hypochlorous acid might not be entirely disso- 
ciated; they may become more hydrolysed with an increase 
in temperature and finally broken down under the influence 
of the carbonic acid liberated from the bicarbonates by heat. 

Chlorine also forms chlorinated organic compounds by 
action on the organic matter present in water and some of the 
objectionable tastes and odours of chlorinated waters have 
been attributed to this agency. Some observers have stated 
that chloramines were amongst the chloro-organo compounds 
produced but the author's experience with the Ottawa supply 
has demonstrated that simple chloramine (NH2CI) can be 
successfully employed for water treatment without causing 
complaints. It was suggested on page 28 that some of the 
higher chloro-amines might be the cause of some complaints 
but at present there is no definite information regarding the 
formation of these compounds in water and all such hypoth- 
eses are little more than conjectures. Letton 1 has reported 
that at Trenton, in 191 1, when the water of the Delaware 
River was first treated, the dosage was as high as 1.2 p.p.m. 
of available chlorine and although chemical tests showed the 
absence of free chlorine, the water had an extremely dis- 
agreeable taste which was especially noticeable in the hot 
water. The conclusion was reached that " the taste and 
odour were not those of chlorine, but were due to some com- 
plex chemical change brought about by the action of the 
chlorine on the organic matter present in the water." 

The waters that require the most accurate adjustment 
of chlorine dosage, if complaints are to be avoided, are these 
containing very small amounts of organic matter. The mar- 
gin between the dosage required for the attainment of a satis- 
factory degree of bacteriological purity and that which may 
cause complaints is usually very small, often less than 25 



COMPLAINTS 65 

per cent, with the waters of the Great Lakes and many filter 
effluents. On the other hand, coloured waters containing 
large amounts of organic matter can be treated with an 
excess of chlorine without causing tastes and odours. The 
author found that the addition of 1.5 p.p.m. of available 
chlorine to the Ottawa River water did not cause complaints 
although only 0.8 to 0.9 p.p.m. were usually required for 
satisfactory purification. Harrington of Montreal has had a 
similar experience with this water. 

The presence of traces of foreign substances in water 
sometimes produces chlorinated derivatives having repugnant 
tastes and odours. Creosote and tar oils have caused an 
odour somewhat resembling that of iodoform and industrial 
wastes have also produced complaints. 

The substitution of chlorine gas (liquid chlorine) for 
bleach solutions has apparently eliminated tastes and odours 
in some cases but this may be due to a more perfect control 
over the dosage rather than to any property of the bleach 
per se. 

In some instances the sludge from bleach plants has 
caused complaints by producing an excessive concentration 
of chlorine during the period of its discharge. This occurred 
in Ottawa on several occasions before it was discovered and 
corrected. When the sludge in the storage tanks reached 
the discharge valve it was customary to wash out the tank 
and discharge the sludge into the river. The operators 
opened the wash out valves to the full extent and the sludge 
and liquor were discharged into the river about 70 feet away 
from the inlet to the sedimentation basin and on the down- 
stream side of it. A portion of the hypochlorite was almost 
invariably carried into the basin and increased the dosage. 
This condition was remedied by carrying the sludge drain 
farther down stream and insisting upon the sludge being dis- 
charged at a slower rate. 

Kienle 2 has reported similar occurrences at Chicago. 



66 CHLORINATION OF WATER 

The hypochlorite was applied at the intake cribs situated a 
considerable distance off shore. The direction of the wind 
often necessitated holding the sludge for a considerable 
length of time but occasionally it was found impossible to 
await favourable conditions with the result that the wind 
and wave action carried a portion of the sludge back into the 
crib and down into the shaft and tunnel. 

The temperature of the water at the time of treatment is 
another factor bearing on the production of tastes and odours. 
When the temperature is low, water absorbs relatively less 
chlorine (vide Diagram No. II, page 38) in the same period 
of time with the consequence that, if the dosage is kept con- 
stant, more chlorine is present in the free condition. At 
Milwaukee (Kienle) 2 with a dosage of 0.24 p. p.m. of available 
chlorine (as bleach) no complaints were received during the 
spring, summer, and autumn seasons but when the temperature 
reached 40 ° F., they were compelled to reduce the chlorine 
to 0.12 p p.m. in order to prevent objectionable tastes and 
odours in the tap waters. 

Abnormal conditions such as freshets, and storms, some- 
times cause complaints regarding tastes and odours. Adams 3 
found that the complaints in Toronto usually accompanied 
a change in the direction of the wind, a sustained east wind 
being the one most productive of trouble. The exact cause 
for this could not be ascertained but it was usually found 
that there was an accompanying increase in the number of 
microscopical organisms (plankton) present in the raw water. 

Freshets usually increase the bacterial contamination and 
necessitate an increased dosage which may cause complaints. 

Complaints as to tastes and odours can be best avoided 
by ensuring regularity of dosage, perfect admixture, and 
storage of the treated water for a reasonable period. These 
factors are discussed in detail elsewhere. 

Colic. Although claims have been made that the con- 
sumption of chlorinated water has produced "colic" no 



COMPLAINTS 67 

corroborative evidence has been adduced and the symptoms 
have probably been due to some other cause. Dilute solu- 
tions of chlorine have been used as intestinal antiseptics in 
the treatment of typhoid fever without producing irritation 
of the mucous lining and the usual dose for this treatment 
is one grain of chlorine. Before taking a medicinal dose 
of chlorine 140 gallons of water containing 0.1 p.p.m. would 
have to be consumed, a quantity greater than is ordinarily 
drunk in a year. 

Chlorine and hypochlorites are destructive and irritant 
to skin and it is possible that hot chlorinated water has, in 
some instances, a similar effect. 

It is inconceivable that the addition of minute traces of 
bleach or chlorine to water should cause it to extract abnormal 
amounts of tannin from tea but it is possible that free chlorine, 
when present, acts upon the tea extractives and produces 
compounds having obnoxious tastes and odours. Tannin 
to the ordinary tea drinker represents the disagreeable por- 
tion of the tea and an obnoxious taste in tea brewed with 
chlorinated water would consequently be ascribed to the 
extraction of abnormal quantities of tannin. 

Almost all waterworks departments using chlorination 
have received complaints to the effect that the water had 
killed fish and small birds. There is usually no evidence 
that the loss was due to chlorinated water but it is generally 
impossible to convince the owners that the process of water 
treatment was not the cause. Many continuous physio- 
logical tests have been made of the effect of chlorinated water 
on small fish and have shown that the concentration used in 
water treatment is without effect. The author kept a tank 
of minnows in one of the pumping stations for months without 
loss although the tank was continuously supplied with water 
that had been treated but a few seconds previously. The bleach 
solution was discharged into the suction of the pumps and the 
water for the fish test was taken from the discharge header. 



68 CHLORINATION OF WATER 

It has been found on many occasions that fish are extremely 
susceptible to chlorine and hypochlorites. This knowledge 
has been sometimes used for such nefarious purposes as fish 
poaching, a few pounds of bleach in a small stream being a 
simple and most effective method of killing all the fish 
which are then carried down stream into a convenient net. 
Chlorinated sewage effluents have also been known to 
destroy the fish life of the stream into which they were 
discharged. 

The opinion of fish culturists as to the action of chlori- 
nated waters upon fish eggs in hatcheries is almost unanim- 
ously to the effect that it is a destructive one. Fish eggs 
are extremely sensitive to chlorine and hypochlorous acid 
and very few will survive in a water containing o.i p.p.m. 
of free chlorine. The Department of Fisheries of the 
Dominion of Canada has informed the author that free 
chlorine in the water had a marked adverse effect on the 
hatching of the eggs of Atlantic salmon, Great Lake trout, 
pickerel, and whitefish but no effect was noticed when free 
chlorine was absent. The Department has, however, decided 
to remove all the hatcheries to localities where water that 
does not require chlorination can be obtained. 

The effect of chlorinated water upon seeds, plants, and 
flowers has been investigated by the Dominion Department 
of Agriculture and Dr. Gussow (Dominion Botanist) and 
Dr. Shutt (Agricultural Chemist) who were in charge of the 
work, have reported that water treated with hypochlorite 
caused no apparent injury to carnations and hybrid roses. 
Six varieties of wheat seed, after soaking in freshly prepared 
hypochlorite solutions (0.05 to 10 parts per million of avail- 
able chlorine) were all sown on the same day. Germination 
was found to be uniform throughout and no effect of the 
chlorine was observed either as regards the rate of germina- 
tion or the development of the young plants. Experiments 
on barley and oats produced similar results. Radishes, 



COMPLAINTS 



69 



turnips, cucumbers, and beans also showed no retardation 
in development after treatment with chlorinated water. 

These experiments were conducted with solutions of bleach 
in distilled water, but identical results were obtained in a 
later series when the treated city supply (Ottawa) was used. 

The results proved conclusively that statements alleg- 
ing damage to plants, flowers, and seeds by the hypochlorite 
treatment of water are unfounded and do not merit the 
slightest consideration. 

Corrosion of Pipes. Chlorinated water, it has been 
alleged on many occasions, causes rapid corrosion of galvanised 
iron water services and especially of the water tubes of boilers, 
water heaters, etc. When bleach is used for water treat- 
ment, a slight increase in the hardness is produced but as 
this is mostly due to calcium chloride, there is no corresponding 
increase in the salts that form a protective coating. The 
presence of traces of calcium chloride and chloro-organic 
compounds might tend to increase the corrosive properties 
of a water but this increase is probably so small as to be 
negligible. 

If pipe corrosion is considered by the carbonic acid hypoth- 
esis, the use of bleach should tend to reduce it because 
bleach contains an excess of base that combines with a por- 
tion of the free carbonic acid. The results of routine tests 
for free carbonic acid made on the raw and treated waters 
at Ottawa are as follows: 





Carbonic Acid. Parts per Million 




Year. 


Raw Water. 


Chlorinated 
Water. 


Nature of Treatment. 


I9f5 
1916 
1917 


1.44 
0.92 
0.84 


1. 41 

O.85 
0.81 


Bleach 
Bleach 

Bleach first four months 
Chloramine during last eight 
months 



70 



CHLORINATION OF WATER 



These figures shown that the hypochlorite treatment pro- 
duced a small but definite decrease in the carbonic acid con- 
tent and should, ceteris paribus, tend to reduce and not in- 
crease corrosion. 

If the corrosion of pipes is considered according to the 
electrolytic theory, a slight increase, due to an increased 
electrical conductivity, might be anticipated. The effect of 
the addition of hypochlorite upon the electrical conductivity 
of distilled water and the Ottawa River water is shown in 
Diagram VI. 

DIAGRAM VI 



5 ■■ 



i-- 



jq 2 



Effect of Calcuim Hypochlorite on Electrical 
Conductivity of Water 20° C. 



. Distilled Water 
-Ottawa River 




Distilled 5 Water 10 15 20 

55 Ottawa River 57.5 60.0 

Conductivity Reciprocal Meg-, ohms 



30 
62.5 



With the concentrations of hypochlorite ordinarily used in 
water treatment it is inconceivable that the slight increase 
in the electrical conductivity has any practical significance 
at low temperatures. The conductivity increases rapidly, 



COMPLAINTS 71 

however, with increase of temperature and any increment 
due to chlorination might produce a slight appreciable effect 
at temperatures approaching the boiling-point of water. 

Liquid chlorine does not increase the conductivity to 
the same extent as an equivalent quantity of hypochlorite 
but it increases the carbonic acid content in proportion to 
the dosage used. 

The author investigated the action cf hypochlorite on 
galvanised pipes in 19 14 and was unable to detect any definite 
corrosion with normal concentrations of chlorine. The experi- 
ments were made with 2 -inch pipes and an examination of 
the first consignment received showed that, although the 
galvanising on the outside was perfect, the inner coat was very 
inferior: in some parts there was an excess of zinc that broke 
away on scraping whilst in others the iron pipe was bare. 

A committee of the Pittsburg Board of Trade, appointed 
to investigate complaints as to pipe corrosion, reported in 
191 7 that they were largely due to inferior qualities of pipes 
and not to the method of water purification employed (slow 
sand filtration and chlorination). 

The effect of chlorination on the plumbo-solvency of water 
was investigated in 1904 by Houston who found that chlorine, 
as chloros, in amounts between one and ten parts per million, 
did not appreciably increase the plumbo-solvent action of 
either unfiltered or filtered water. Similar results were 
obtained by the author with the Toronto supply: raw lake 
water, filtered water, and water treated with 0.25 and 0.50 
p. p.m. of chlorine, all dissolved the same quantity of lead in 
twenty-four hours. The amount in each case was too small 
to be of any significance. 

BIBLIOGRAPHY 

(1) Letton. J. Amer. Waterworks Assoc, 1915, 2, 688. 

(2) Kienle. J. Amer. Waterworks Assoc, 191 5, 2, 690. 

(3) Adams. J. Amer. Pub. Health Assoc, 1916, 6, 867. 



CHAPTER VI 

BLEACH TREATMENT 

The treatment of water with bleach alone has been largely 
supplanted by the liquid chlorine process but the following 
details will be of use on meeting conditions for which liquid 
chlorine cannot be used and also for the preparation of the 
hypochlorite solution required in the chloramine process. 

The essential features of a bleach installation are the 
solution or mixing tanks, storage tanks, piping system, dis- 
charge orifice or weir, and sludge drain. 

Bleach is usually sent out by the manufacturers in sheet 
steel drums, 39 inches high and 29! inches in diameter, which 
contain about 14 cu. ft. of bleach and weigh approximately 
750 pounds gross and 690 pounds net. It can be most 
economically purchased in car lots and if the consumption 
warrants this procedure storage should be provided for about 
70 drums or rather more than one car load According to 
Hooker x bleach loses 1 per cent of available chlorine per 
month in hot seasons and 0.3 per cent in cold ones so that it 
is advisable to carry as little stock as possible during hot 
weather. Hot weather also causes a further loss by accel- 
erating the action of the bleach on the drum which rapidly 
disentegrates and cannot be handled. Bleach can often be 
purchased more cheaply in hot weather but such a policy is a 
short sighted one unless it is required for immediate use. 

The general design of a hypochlorite plant is largely deter- 
mined by the capacity but in all cases an effort should be made 
to avoid complicated details which may appear advantageous 

72 



BLEACH TREATMENT 73 

in the drafting office but do not stand up in actual practice. 
Many metals rapidly develop a protective coating on immer- 
sion in bleach solution but if this is removed by friction, 
rapid erosion ensues; bearing metallic surfaces should be 
reduced to a minimum. 

Mixing Tanks. All tanks, whether mixing or storage, 
should be constructed of concrete and painted with two 
coats of asphalt. Experience has shown that wooden tanks 
are not suitable. The author has used pine, oak, and cypress 
tanks but all were rapidly leached by the hypochlorite and 
ultimately had to be lined with concrete. 

There is a considerable variation in the concentration of 
bleach solution made in mixing tanks at various works. 
Some operators use about one gallon of water per pound of 
bleach and mix the two to a cream by wooden paddles, 
revolving on a central axis, for 1-2 hours; the paddles are 
then stopped and the cream run out into the storage tanks 
and diluted to the required strength by passing water through 
the mixing tank. There are two objections to this method: 
(1) the addition of small quantities of water to bleach tends to 
gelatinisation which may protect lumps from the further 
action of water and (2) a stratification of the solution occurs 
in the storage tank unless agitation is used. Gelatinisation 
causes loss of available chlorine and stratification causes 
irregular dosage unless corrected by agitation, which necessi- 
tates power. Other operators mix the bleach and water to 
the final concentration in the mixing tank and discharge the 
contents into the storage tank, the intermittent process being 
repeated until the storage tank is full. Gelatinisation is 
avoided by using a low original concentration and as all 
batches are of equal density no stratification is produced. 

At Ottawa the bleach is crushed and, after weighing, 
dumped into a circular concrete tank provided with a hinged 
wooden lid. The stirring arrangement consists of a bronze 
shaft on which an aluminium impeller is fixed which revolves 



74 



CHLORINATION OF WATER 



in an iron tube set slightly above the bottom of the tank 
(see Fig. i). After the requisite amount of water has been 
added the motor connected to the bronze shaft is started 
and the mixture pumped for 15-20 minutes; without waiting 
for the sludge to settle the contents are discharged into the 
storage tank and the operation repeated until the tank is 
full. The piping between the mixing and storage tanks is of 
galvanised iron of generous dimension so as to compensate 




Water supply 



Steam coil 



Fig. i. — Mixing Tank for Bleach. 



for incrustation. The pipes are straight and are provided 
with crosses at every change of direction to enable excessive 
incrustation to be removed. The valves should be made of 
hard rubber or special bronze; if brass valves are used they 
will probably require renewing every twelve months. 

The concentration of solution necessarily depends upon 
local conditions but it is usually advisable to keep it below 
2.5 per cent of bleach, which is equivalent to 0.85 per cent 
of available chlorine. 



BLEACH TREATMENT 75 

Storage Tanks. These should be built of reinforced con- 
crete and painted inside with asphalt, which should be periodi- 
cally renewed to prevent the solution seeping through to the 
reinforcement. At least two tanks should be provided 
so that one may be filled and allowed to settle before being 
put in operation. The hypochlorite discharge pipe is usually 
6-9 inches from the bottom to permit the collection of sludge, 
which is run off when it reaches the elevation of the hypo- 
chlorite discharge. The sludge drain, which opens into the 
bottom of the tank, is usually a 4- or 6-inch cast-iron pipe, 
with suitable gate valve, which discharges into a common 
drain made of clay pipe. 

The storage tanks should be provided with either glass 
gauges or float indicators to enable the orifice discharge 
to be checked up at periodical intervals. 

Regulation of Dosage. The discharge of the hypochlorite 
solution is usually regulated either by maintaining a constant 
head on an orifice of variable dimension or by varying the 
head on an orifice of fixed dimension. The weir principle 
may also be used but it is not so well adapted for hypochlorite 
as for other chemicals. 

In the constant head method, the head is maintained by a 
bronze valve connected to a float made of glass or tinned 
copper. In many cases the orifice is a rectangular slot in a 
brass plate and is adjusted by means of a brass slide operated 
by a micrometer screw. Brass plates are not very suitable 
as they become corroded and so reduce the size of the orifice; 
if the incrustation is removed the orifice will discharge more 
than the calibration indicates. Needle valves are unsuit- 
able for similar reasons. 

An example of an orifice feed box of the constant head 
type is shown in Fig. 2. A vertically arranged hard-rubber 
pipe passes through a hard rubber stuffing box in the bottom 
of the tank and has one or more orifices near its upper end. 
The area of the submerged portions of the orifices is controlled 



76 



CHLORINATION OF WATER 



by the hand wheel which is connected with the threaded stem 
of the pipe. The stem has sixteen threads per inch, and one 





1 



/ . ■■ 



Fig. 2. — Dosage Tank. 

revolution of the wheel will submerge the orifices one-sixteenth 

of an inch. The extent to which the orifices are submerged 

is indicated on the dial fixed to the side of 

the tank. 

Fig. 3 shows the regulating mechanism 

of another apparatus of the constant head 

type. The orifice consists of a circular 

slot in a hard rubber disc and is regulated 

by means of a hand wheel which operates 

a hard rubber slide. 

The general arrangement of one of the 

variable head types is shown in Fig. 4. A 

constant head is maintained on the valve 

V by a float and cock operating in a lead- 

or porcelain-lined tank. The circular 

tapered orifice 0, cut in glass, is situated 

in the flanged end of the iron casting C and 

the head, indicated on the gauge glass, is 

„ r, .,, „ regulated by valve V. This arrangement 

Fig. 3. — Orifice Con- . 

trolling Device. is simple and reasonably accurate. The 




BLEACH TREATMENT 



77 



orifice may show slight incrustation after being in service 
for some time but it can be easily cleaned by means of a 
test-tube brush or a small swab moistened with acid; a 
wire or rod tends to break the edge of the conical orifice 
and should not be used. 

The volume of solution discharged by orifices of various 
dimensions is shown in Diagram XV, page 149. Diagram 
XVI, page 149, facilitates the calculation of the number of 
pounds of bleach required for any dosage. 




Fig. 4. — Variable Head Dosage Box. 



The solution discharged from the orifice box is carried 
to the point of application either in galvanised iron pipes of 
generous dimension or in rubber hose. Pumps may be used 
for raising the solution to a higher elevation but unless 
special material is used in their construction they corrode 
rapidly and cannot be kept in service. Whenever possible, 
a water injector should be used as it does not corrode and 
assists in maintaining the delivery pipes free from sludge. 
All delivery pipes should be duplicated and blown out regularly 
by water under pressure; they should also be protected from 
frost. 

The adjustment of the hypochlorite dosage can be auto- 
matically regulated in plants where the flow of the water to 
be treated is measured by a Venturi meter or other suitable 



78 CHLORINATION OF WATER 

appliance. Various devices have been suggested and used 
but, in general they are not so successful as automatic regu- 
lators for liquid chlorine on account of the presence of sludge 
particles which tend to diminish the area of the orifice. 

For small plants, barrels have often been used as solution 
and storage vessels with, in some instances, fairly successful 
results. The bleach process, however, cannot be recommended 
for small installations because the chemical control necesary 
for successful operation is usually not available. One drum 
of bleach may suffice for several months operation and as the 
powder gradually loses strength, the dosage constantly dimin- 
ishes and may jeopardise the safety of the supply. Liquid 
chlorine machines are much more suitable than hypochlorite 
installations for supplies having no chemical control. 

Bleach is being very extensively used for the sterilisation 
of the water used by the allied troops in France. The 
water supplies on the British front are all more or less subject 
to pollution and it is consequently necessary, to ensure 
adequate protection, to chlorinate all supplies with bleach. 
Other forms of chlorine have been tried but have not proved 
successful near the firing lines. The details of the technique 
employed cannot be given but it may be stated that the con- 
centration of chlorine employed is always more than sufficient 
and that residual tastes and odours are regarded as secondary 
considerations. Treated water is always tested by the starch- 
iodide method and a bacteriological examination is frequently 
made by mobile laboratories 

Control of Hypochlorite Plants. If efficient operation and 
regular dosage is to be obtained, it is necessary that hypo- 
chlorite plants should be controlled by a trained chemist. 
Good results are occasionally obtained without such control 
but in every plant circumstances arise at some period or 
another which only a chemist is qualified to deal with. 

The points that require consideration are (i) the com- 
position of the bleach; (2) concentration of available chlorine 



BLEACH TREATMENT 79 

in the prepared solutions; and (3) chemical tests for free 
chlorine in the treated water. 

(1) Composition of Bleach. Each drum of bleach should be 
sampled and analysed before use. The sample is obtained 
by cutting out the head of the drum and removing a vertical 
section by means of a special sampling tube or a piece of half- 
inch iron pipe which is forced to the bottom of the drum 
with a boring motion and then removed; the core is then 
forced out by means of a rod, mixed, and quartered down to 
the required size. 

For analysis weigh out 5 grms. on a balance sensitive 
to 0.01 grm. and grind in a mortar with 50-70 c.cms. of water; 
wash into a 250 c.cm, flask and make the volume up to 250 
c.cms.; shake. After allowing the sludge to settle remove 
10 c.cms. by means of a pipette and titrate by one of the 
following methods: 

Bunsen's Method. Add 10 c.cms. of a 5 per cent solution 
of potassium iodide and 0.5 c.cm. glacial acetic acid and 
titrate with sodium thiosulphate (24.8 grms. of the C.P. 
crystalline salt and 1 c.cm. of chloroform per litre) using a 
starch solution as indicator. Each cubic centimetre of thio- 
sulphate used = 1.755 P er cen t of available chlorine (1 c.cm. 
N/10 sodium thiosulphate = 0.00355 grm available chlorine) 

Penofs Method. Dilute the hypochlorite solution with 
15 c.cms. of water and titrate with a solution of N/10 sodium 
arsenite using starch-iodide paper as an external indicator. 
Each c.cm. of solution used = 1.755 P er cen t °f available 
chlorine (1 c cm =0.00355 grm. available chlorine). The 
use of an external indicator makes this process a slow one 
and to overcome this objection Mohr proposed the addition 
of an excess of sodium arsenite solution and then titrating 
with N/10 iodine solution after adding a few drops of starch 
solution. 

Griffen and Hadallen 2 compared these three methods 
and found that Penot's method and Mohr's modification of 



80 CHLORINATION OF WATER 

that method gave results which were 0.6 per cent lower than 
those obtained by Bunsen's method. 

For a separate estimation of the chlorine present as 
chloride, chlorate, and hypochlorite the method given in 
Sutton's Volumetric Analysis, 10th edition, page 178, should 
be followed. 

Storage Liquor. This .is tested by any of the above 
methods. It has been proposed to determine the strength 
of the bleach solution by the use of a hydrometer but the 
results are not sufficiently accurate and the method cannot be 
recommended. 

If bleach is properly broken up and thoroughly agitated 
in the mixing tank at least 95 per cent of the available chlorine 
should be extracted. The efficiency of the extraction process 
is checked by comparing the tests of the storage liquor with 
those of the dry bleach and each batch of liquor should be 
tested daily. It is sometimes advisable to take two samples 
from each tank, one soon after a tank has been put into 
operation, and a second sample at the end of the run. Con- 
siderable differences are occasionally found between these 
samples and are due, either to inadequate agitation of the 
liquor in the storage tank, or inefficient mixing in the mixing 
tank. If the results are irregular the former is the more 
probable cause but if the second sample is invariably stronger 
the mixing tank operations should be investigated. The 
increased concentration of the second sample is due to unex- 
tracted bleach passing out of the mixing tank and gradually 
becoming leached as the tank contents are run off. If the 
bleach is lumpy and is not subsequently broken up, losses 
are almost inevitable. 

Hale 3 found that during the period when the New York 
City supply was being treated with bleach it was necessary 
to constantly check the operations of the labourers by frequent 
samples. "'During one week about 95 per cent of the chlorine 
added was actually applied, the second week it dropped to 



BLEACH TREATMENT 81 

85 per cent, and the third week to 75 per cent. Whenever a 
poor run is called to the attention of the labourers, results 
improve." 

By taking two samples daily from each tank discharged 
the author has been able to obtain an average annual efficiency 
on the Ottawa plant of 94 per cent, i.e. the solutions contained 
94 per cent of the available chlorine contained in the bleach. 
In making such checks it is necessary to keep a careful account 
of the stock of bleach to prevent labourers adding a few extra 
pounds of bleach to compensate for losses. 

Sludge forms an appreciable but unavoidable source of 
loss of material. When the sludge reaches the outlet of the 
hypochlorite pipe the sludge must be run to waste; otherwise 
it will pass over and tend to choke the dosage control appara- 
tus. If the sludge is run into the same body of water that 
forms the source of supply, it must be discharged very slowly 
to prevent a possibility of over dosage and damage to fish 
life With proper control, sludge losses can easily be kept 
under 2 per cent and often under 1 per cent. 

The greatest source of unavoidable loss in hypochlorite 
plants is from deterioration of the bleach during storage; 
in warm climates this loss may exceed 10 per cent. In 
Ottawa where high temperatures are only experienced during 
the summer months the loss from this cause has averaged 
from 7-8 per cent on the bleach stored during that period. 

Detection and Estimation of Free Chlorine. The oldest 
and probably the best known test for free chlorine in water 
is the Wagner test, made by adding a few drops of potassium 
iodide and starch; the presence of chlorine is indicated by a 
deep rich blue colouration that is proportional in intensity 
to the quantity of chlorine present. When this test is used 
as a colorimetric method for the estimation of chlorine several 
difficulties are encountered; the intensity of the colour pro- 
duced by the majority of treated waters gradually diminishes 
and the loss is usually more rapid than in the standards 



82 CHLORINATION OF WATER 

made up with distilled water; a different result is obtained 
if the solutions are acidified and the results vary with dif- 
ferent acids acetic acid yielding a much lower result than a 
mineral acid such as hydrochloric acid; in the presence of 
acid the colouration usually intensifies on standing, whereas 
the standard intensifies but little. The difference caused by 
the addition of acid is imperfectly understood but it is obvious 
that the chlorine set free by the acid cannot be present in 
the "free" state; it is probably in a semi-labile condition 
loosely attached to organic compounds. Whether this semi- 
labile chlorine is available for germicidal action is at present 
not definitely known but it has been noted by several observers 
that the germicidal action proceeds after the " free" chlorine 
reaction has disappeared. 

The method used by the author for the estimation of 
free chlorine is as follows: place 500 c.cms. of the sample 
in a stoppered bottle, add 1 c.cm. of 5 per cent KI solution, 
2 drops of cone. HC1 and 1 c.cm. of starch solution and titrate 
with N/1000 sodium thiosulphate until colourless. The dif- 
ficulty introduced by the opalescence of the liquid is over- 
come by pouring portions of the liquid into two Nessler tubes 
and adding a drop of thiosulphate solution to one and noting 
if any reduction of colour occurs on shaking; if the intensity 
of the colour is diminished, the contents of both tubes are 
poured back into the bottle and titrated until no further 
colour removal, as shown by the tubes, can be obtained. 
One c.cm. of N/1000 sodium thiosulphate = 0.07 p.p.m. of 
available chlorine when 500 c.cms. of water are used. 

Adams 4 has employed the colorimetric method of estimat- 
ing the colour obtained after the addition of dilute H2SO4, KI, 
and starch but used standard solutions of dyes for compari- 
son. The standards were prepared from mixtures of Bril- 
liant Mill Green " S" and Cardinal Red " J" and were made 
up weekly. 

Phelps found that ortho-tolidine in acetic acid solution 



BLEACH TREATMENT 83 

produced an intense yellow colouration with free chlorine, 
and suggested the use of this reagent as a qualitative test 
for chlorine. Ellms and Hauser 5 developed this process 
into a quantitative one and substituted hydrochloric acid 
for acetic acid as a solvent. One c.cm. of the reagent (i gram 
of pure o-tolidine dissolved in i litre of 10 per cent of hydro- 
chloric acid) is added to ioo c.cms. of the sample in a Nessler 
tube and the colour compared after five minutes with per- 
manent standards made up with mixtures of potassium 
bichromate and copper sulphate. This method was adopted 
as the official standard method of the American Public Health 
Association; the details are given in the Appendix (p. 147). 

The author has found that this method gives excellent 
results except for coloured waters. The colouring matter 
in many waters diminishes in intensity on the addition of 
acids and is somewhat similar in tint to that produced by 
addition of 0-tolidine. If the reaction is used qualitatively 
on coloured treated water and a comparison made with the 
untreated sample, a negative result, due to the reduction in 
colour produced by the acid being greater than the increase 
caused by the reagent, might be obtained when traces of free 
chlorine are present. Similar difficulties are encountered 
when quantitative comparisons are made against permanent 
standards. 

Benzidine (Wallis 6 ) has also been suggested for the 
detection of free chlorine. On adding this reagent a blue 
colouration is produced but on stirring it rapidly changes to a 
bright yellow which is proportional in intensity to the amount 
of free chlorine present Ellms and Hauser 5 investigated 
benzidine in 19 13 and found it to be inferior to o-tolidine as 
a test reagent for free chlorine. 

LeRoy 7 has proposed the use of hexamethyltri^ara- 
aminotriphenylmethane for detecting and estimating free 
chlorine. On the addition of a hydrochloric acid solution 
of this compound to a sample containing free chlorine a 



84 CHLORINATION OF WATER 

violet colouration is produced that can be matched in the usual 
way with standards. It is stated that 0.03 p.p.m. of free 
chlorine gives a distinct colouration and that the reagent 
reacts very slowly with nitrites and is quite unaffected by 
hydrogen peroxide. 

The starch-iodide and 0-tolidine reactions are affected 
by oxidising agents or reducible substances; nitrites and 
ferric salts are the compounds that are most likely to inter- 
fere and Ellms and Hauser 5 have found that these bodies do 
not affect the 0-tolidine reaction to the same extent as the 
starch-iodide reaction. Very small quantities of nitrites (0.03 
p.p.m. of N) and ferric salts (0.2 p.p.m. Fe) give a blue 
colouration with the starch-iodide reagent and for this reason 
it is always advisable, whenever possible, to make a control 
test on the untreated water. Nitrites are oxidised by free 
chlorine and consequently do not interfere with the estima- 
tion of it by the thiosulphate method; the influence of ferric 
salts can be overcome by substituting 3 c.cms. of 25 per cent 
phosphoric acid for hydrochloric acid (Winkler 8 ) . 

An electrical instrument called a " chlorometer" has been 
devised by E. K. Rideal and Evans 9 for the estimation of 
free chlorine. The 'diagrammatic sketch, reproduced in Fig. 
5, shows the general construction of the apparatus. When 
water containing no free chlorine passes through the copper 
tube, hydrogen is liberated on the platinum rod by the elec- 
trolytic solution pressure of the copper and an electric current 
is generated; a polarizing action follows and the flow of 
current ceases. When free chlorine is present it combines 
with the hydrogen as produced and so enables more copper 
to dissolve and produces a permanent flow of current. The 
current produced is a function of the depolarizing action, i.e. 
of the free chlorine, and is indicated by the current meter 
which is graduated in parts per million of available chlorine. 
The usual range of instrument is 5 p.p.m. and each division 
of the scale is equal to one-tenth of one part per million. 



BLEACH TREATMENT 



85 



Only strong oxidisers, such as chlorine, ozone, and per- 
manganates, which have a great affinity for hydrogen, 
are able to produce a permanent current; ferric chloride 
and other weak oxidisers do not affect the indicator. 



Costs 

Cost of Construction. According to the replies received 
by the Committee on Water Supplies of the American Public 



■+— / VAAA/ — 

To Current Measurer 

— vww — 



B' —> 

?illllMIIIINIIIIIINIIIIIIIIIII 




C — Copper Tube. 
P— Platinum Rod. 
E E— Ebonite Caps. 
T T — Terminals. 
B.B— Insulated Metal 

Tubes. 
BB'- Taps. 
K — Plug Switch* 
A-A' — Entrance and Exl£ 

to Centre-.piece. 

I 1 Insulator. 

r E~ WB 1 Metal, 

Fig. 5. — Rideal-Evans Chlorometer. 

Health Association 10 the total cost of equipment for disin- 
fection varies widely and bears no apparent relation to the 
capacity of the equipment. This is due to the temporary 
nature of the plants erected in many cities and the necessity 
of erecting expensive structures in others. The cost of con- 
struction varies also in different localities. The cost of equip- 
ping hypochlorite plants with standard concrete tanks and 
dosage regulators would be more uniform and for capacities 
between 10 and 50 million gallons per day would approximate 
$15 to $50 per million gallons. 



86 CHLORINATTON OF WATER 

The operating cost of bleach plants shows similar wide 
variations. In some cases the labour required for mixing 
and supervision can be obtained without extra cost whilst 
in others the labour charge exceeds the cost of hypochlorite. 

The price of bleach has shown violent fluctuations during 
the last three years (see Diagram IX, page 125) but is now 
(1918) comparatively steady at $2.25 to $2.75 per 100 pounds. 
Assuming that 33.3 per cent of available chlorine can be 
extracted; each pound of chlorine costs 6.75-7.25 cents as 
compared with 15-25 cents for liquid chlorine. The fixed 
charges on the capital expenditures together with the labour 
and incidental charges almost invariably make the total 
cost of operation of a straight bleach plant higher than that 
of a liquid chlorine plant. The tendency during the last 
four years. has been to substitute liquid chlorine for hypo- 
chlorite and the majority of the plants are now of the former 
type. 

"Antichlors" 

Substances used for the removal of excess chlorine are 
usually known as ' antichlors" and those that have been 
most frequently employed are sodium bisulphite, NaHSOs, 
and sodium thiosulphate Na2So03. The reactions with 
chlorine are: 

(i) NaHS0 3 +Cl2+H 2 = NaHS04 + 2HCl. 

(ii) Na 2 S203+Cl2 = Na2S 4 6 +2NaCl. 

Sodium bisulphite is a very efficient " antichlor," only 1.46 
parts being required to remove 1 part of chlorine, but owing 
to its instability the action is uncertain. Sodium thio- 
sulphate is a comparatively stable cheap salt, containing 5 
molecules of water of crystallization, Na2S203-5H20 but 
7 parts are necessary to remove 1 part by weight of chlorine. 
"Antichlors" are used as aqueous solutions and the 
dosage controlled in the same manner as for bleach solutions. 



BLEACH TREATMENT 87 

The action is an instantaneous one and it is consequently 
necessary that the germicidal action should be complete 
before the "antichlor" is added. 

Filters, containing solid materials capable of absorbing 
free chlorine, have also been used for removing the excess 
of the germicidal reagent. Iron borings and aluminium 
were used experimentally by Thresh n but the process was 
not commercially developed. The "De Chlor" filter, in 
which carbon is the active substance, has been installed at 
several water works in England (Reading, Exeter, Aldershot) 
with apparently successful results. The Reading experimental 
installation, described by Walker, 12 consisted of a steel 
drum, 8 feet 3 inches in width, the top and bottom being 
domed. In the upper portion, 10 feet 9 inches in depth, pro- 
vision was made for thorough admixture of the bleach solu- 
tion and water and a subsequent storage of thirty minutes. 
The lower section of the filter was divided into three com- 
partments, the first and last of which contained graded 
silica; the middle compartment was filled with a layer (20 
inches deep) of specially prepared granulated charcoal or 
carbon. 

The filter was operated under pressure and passed an 
average of 192,000 Imp. gallons per day, the rate being 
32,000 Imp. gallons per square yard per day. 

Water from the pre-filters (polarite and sand) was treated 
with bleach to give a concentration of 1 p.p.m. of available 
chlorine and passed through the De Chlor filter. The average 
bacteriological results obtained during the first six months 
operation were as follows: 

Bacteria Per c.cm. B. coli Index 

Gelatine 3 Days at 20° C. Per 100 c.cms. 

Raw river water 6,775 600 

Water from pre-filters 579 119 

Water from De Chlor filter 33 Nil 

Free chlorine could not be detected by chemical tests 
in the filtered water which was also free from abnormal 



88 CHLORINATION OF WATER 

tastes and odours. It is stated that the carbon has to be 
removed and revivified periodically. The filter was washed 
about once per week, the wash water being only one-tenth 
of one per cent. 

The experimental filter was operated for nearly two years 
before being removed to permit the erection of larger units 
having a total capacity of one million Imp. gallons per day. 

BIBLIOGRAPHY 

(i) Hooker. Chloride of Lime in Sanitation, New York, 1913. 

(2) Griffen and Hedallen. J. Soc. Chem. Ind., 1915, 34, 530. 

(3) Hale. Proc. N. J. San. Assoc, 1914. 

(4) Adams. J. Amer. Pub. Health Assoc, 1916, 6, 867. 

(5) Ellms and Hauser. J. Ind. and Eng. Chem., 1913, 5, 915 and 1030; 
ibid., 1914, 6, 553. 

(6) Wallis. Ind. lour. Med. Res., 191 7, 4, 797. 

(7) Le Roy. Comptes rend., 1916, 163, 226. 

(8) Winkler. Zeit. angew. Chem., 1915, 28, 22. 

(9) Rideal, E. K. and Evans. Analyst, 1913, 38, 353. 

(10) J. Amer. Pub. Health Assoc. 1915, 5, 921. 

(11) Thresh. Internat. Congress Appl. Chem., 1908. 

(12) Walker. Jour. Roy. Inst. Pub. Health, Jan., 191 1. 



CHAPTER VII 
LIQUID CHLORINE 

The use of liquefied chlorine for the disinfection of water 
was first proposed by Lieutant Nesfield * of the Indian Medical 
Service. He stated that: " It occurred to me that chlorine 
gas might be found satisfactory ... if suitable means could 
be found for using it. . . The next important question was 
how to render the gas portable. This might be accomplished 
in two ways: By liquefying it, and storing it in lead-lined 
iron vessels, having a jet with a very fine capillary canal, 
and fitted with a tap or a screw cap The tap is turned on, 
and the cylinder placed in the amount of water required. 
The chlorine bubbles out, and in ten to fifteen minutes the 
water is absolutely safe, and has only to be rendered tasteless 
by the addition of sodium sulphite made into a cake or 
tablet. . . The cylinders could, of course, be refilled. This 
method would be of use on a large scale, as for service water 
carts." 

The first practical demonstration of the possibilities of 
this method was made by Major Darnall 2 of the Medical 
Corps, United States Army, in 1910. Chlorine was taken 
from steel cylinders and passed through automatic reducing 
valves which provided a uniform flow of gas for the water 
requiring treatment. A uniform flow of water was main- 
tained through the mixing pipe and so secured a uniform 
dosage. This apparatus might be considered as the fore- 
runner of the various commercial types of machines that were 

89 



90 CHLORINATION OF WATER 

developed later and which are being so extensively used at the 
present time. 

A working model, having a capacity of 500 gallons per 
hour, was erected at Fort Myer, Va., and' was operated on 
water that had been treated with alum but had received no 
further purification. Despite the presence of the flocculated 
organic matter, satisfactory purification was obtained with 
0.5 to 1.0 p.p.m. of available chlorine and no taste or odour 
was imparted to the supply. 

From the results obtained at Fort Myer, and Washington, 
D. C, Darnall concluded that " In general, it may be said 
that with an average unfiltered river water such as that of the 
Potomac, about one-half of one part (by weight) of chlorine 
gas per million of water will be required. For clear lake 
waters three-tenths to four-tenths of a part per million will be 
sufficient." 

A Board of Officers of the War Department examined 
the results and reported (June, 191 1) "That the apparatus 
is as efficient as purification by ozone or hypochlorite and is 
more reliable in operation that either. . . . That it could 
be installed at a very low clost and that the cost of operation 
would be very slight." 

In June, 191 2, Ornstein experimented with chlorine gas, 
obtained from the liquefied gas in cylinders, for sewage and 
water disinfection but his method differed from Darnall's 
in first dissolving the gas in water and feeding the solution to 
the liquid to be treated. 

Kienle 3 made experiments at Wilmington, Del., in No- 
vember, 191 2, and obtained a constant flow of gas by means 
of high- and low-pressure valves; the gas was dissolved in 
water in an absorption tower and afterwards fed to the water 
to be treated. 

Van Loan and Thomas of Philadelphia experimented 
with liquid chlorine on a large scale at the Belmont Filter 
Plant in September, 191 2. The chlorine was fed into the 



LIQUID CHLORINE 91 

filtered water basin in the gaseous state and the quantity 
was regulated by the loss in weight of the containers. The 
dosage was approximately 0.14 p.p.m. (West 4 ). 

Jackson, of Brooklyn, made similar experiments about 
the same time at the Ridgewood Reservoir, Brooklyn, and 
his type of apparatus was shortly afterwards put on the mar- 
ket as the Leavitt- Jackson Liquid Chlorine Machine. The 
regulation of the flow in this machine was determined by 
the loss in weight of the gas cylinder which was suspended 
from a sensitive scale beam. By moving the counterbalanc- 
ing weight on the beam at a constant rate, a uniform flow 
of gas was obtained, the area of the orifice being kept constant 
by the equilibrium in the balance operating controlling valves 
through a system of levers. 

This type of apparatus was tried at several places but it 
was found that the adjustment of the regulating mechanism 
was too sensitive and produced considerable irregularities 
in the flow of gas. 

The type used by Ornstein and Kienle were combined 
and commercially developed by the Electric Bleaching Gas 
Co. of New York.* In this combined type the gas was col- 
lected from one or more cylinders by means of a manifold 
which delivered it to the regulating mechanism at the pres- 
sure indicated by a gauge attached to the inlet pipe. Beyond 
this gauge were two pressure-regulating devices, the first 
being used primarily to reduce the initial pressure to about 
15 pounds per square inch, and the second for controlling the 
pressure through a range sufficient to give the desired dis- 
charge of gas. The gas from the second regulator passed 
through an orifice in a plate at a pressure indicated by a 
suitable gauge which was calibrated in terms of weight of 
chlorine per unit of time. The gas, on leaving the regulating 
apparatus, passed up an absorption tower of hard rubber, 
where it met a descending stream of water. The solution 
* This type has recently been withdrawn from the market. 



92 



CHLORINATION OF WATER 



was carried by suitable piping to the point of application. 
This type was modified in some cases by the substitution 
of a flow meter of the float type for the inferential pressure 
meter. 



Chlorine Check Valve 
Solution Jar Head 
Jet Orifice Cleaner 
Feed Water Gage 
Strainer 



Water Pressure 
Seducing- Valve 

Feed Water Valve 
Feed Water 
Supply Line 
Solution Jar 
Check Valve 
Pulsating Meter 
Solution Outlet Tube 
Water Seal 
Water Seal Overflow 
Solution Line 
Tank Valve 
Valve Yoke 
Chlorine Tank 




Tank Pressure Gage 



Chlorine Control 
Valve 



Compensator Cap 



Pressure 
Compensator 



Flexible Tank 
Connection 



Auxiliary Tank 
Valve 



Fig. 6. — Manual Control Chlorinator, Solution Feed, Type A. 

Another type of apparatus, developed by Wallace and 
Tiernan,* is shown in Figs. 6 and 7. The gas under the 
pressure indicated by the tank pressure gauge (Fig. 6) 
passes into the pressure compensating chamber, which main- 
tains a constant drop in pressure across the chlorine control 
* Manufactured by Wallace and Tiernan Co. Inc. N. Y. 



LIQUID CHLORINE 



93 



valve, through the check valve, and into the solution jar 
after measurement in the pulsating meter. The water 
required for dissolving the chlorine enters the jar through 
the feed line and check valve and the solution passes along 
the feed line after being water sealed in a special chamber. 



Feed Water 

Gauge 
Ga uge Co ck 

Chlorine 
Che ck Val ve 

Solution 

Ja r Head 
Feed Water 

Valve 
Sol ution Jar 

Solution ■ 
Out let Tu be 
Feed Water 
Supply Line" 




Back Pressure 

Gauge 
Blow-off Valve 



fj Manometer 
Fill ing Scr ew 
Glass Orifice 
Glass Orifice 

Cap 

Ma nome ter 

Scale 

Con trol V alve 

Cont act Sp ring ' 

Co ntact A rm 

Tank Pressure 

Gauge 

Comp ensato r Cap' 

Solution Line 



Flexible Tank Connections 
Tank Valves 
Auxiliary Tank Valves 
Valve Yokei 
CMorine Tanks 




Fig. 7. — Manual Control Chlorinator, Solution Feed, Type B. 



The meter is a volumetric displacement one and is regulated 
by observing the number of pulsations per minute. Each 
pulsation corresponds to 100 milligrams or 0.00022 pound 
of chlorine; diagrams for converting pulsations per minute 
into weight per twenty-four hours are usually provided 



94 CHLORINATION OF WATER 

with the apparatus. This type of meter is suitable for 
quantities between o.i and 12 pounds per day and possesses 
the distinct advantage of enabling the operator to see the 
actual delivery of the gas. 

The quantities of gas exceeding 12 pounds per day the 
type shown in Fig. 7 may be used. The gas from the 
control valve passes through a visible glass orifice which is 
connected with the manometer. This manometer, or chlo- 
rine meter, contains carbon tetrachloride and is graduated 
empirically in terms of weight of chlorine per unit of time. 
A suitable gauge indicates the back pressure thrown by the 
check valve and registers the same pressure as the tank 
gauge when the flow of gas is stopped. The gas passes into 
the glass cylinder where it is dissolved in water and passes 
out by the feed pipe. 

The most accurate range of the orifice type is from 1-6, 
i.e. if the minimum graduation on the scale is 10, the maxi- 
mum is 60. If quantities less than the minimum graduation 
are desired, a smaller orifice with its corresponding scale 
can be substituted in a few minutes. 

These types are manually controlled, but automatic con- 
trol types, to meet almost any condition, can be obtained 
and are in use in many cities. 

In some instances (dry-feed types) the chlorine gas is 
not dissolved in water prior to addition to the water requiring 
treatment but is carried to the point of application as a dry 
gas and enters the water through a diffusion plate made of 
carborundum sponge. The sponge becomes saturated with 
water because of the capillary action of the carborundum 
upon the water. The pressure of the chlorine in the feed 
pipe forces the gas through the diffuser in the form of minute 
bubbles which become saturated with moisture On meeting 
the water they immediately go into solution and no gas 
escapes. 

The operation of liquid chlorine machines is exceedingly 



LIQUID CHLORINE 95 

simple. After the cylinders have been connected, the cylinder 
valves are opened and the joints tested for leakage by holding 
a swab of absorbent cotton saturated with strong ammonia 
under them; a leakage is indicated by the appearance of 
white fumes of ammonium chloride. The control valve is 
then slightly opened and the auxiliary cylinder valves par- 
tially opened; whilst the pressure in the apparatus is slowly 
increasing the remainder of the joints are tested and if found 
to be tight, the cylinder valves are fully opened and the control 
valve opened to the desired amount. In the solution feed 
types the water required as solvent is turned on before the 
control valve is opened. Once the apparatus is working, 
no further attention is required, except for the regulation 
of the dosage in the manual control types, until the cylinders 
are replaced. When the stock of gas in the cylinders is 
almost depleted the pressure falls but it is always preferable 
to determine the stock by standing the cylinders on a plat- 
form scale and weighing at regular intervals. This also 
provides a check on the apparatus and can be utilised to 
check the operators. 

The accumulation of substances that impede the flow of 
gas is usually slow and is indicated by a gradual increase 
in the back pressure. The orifice is calibrated at 25 pounds 
back pressure and any deviation from this figure will show a 
discrepancy between the actual weight of chlorine evaporated 
and the amount calculated from the scale reading. 

Liquid chlorine is usually sent out by the manufacturers 
in steel cylinders which contain about 1.1 cubic feet of liquid 
or approximately 100 pounds (1 cu. ft. =89.75 pounds).* 

For small installations only one cylinder is necessary 
but it is always preferable to connect more than one. When 
the flow of gas is rapid the temperature of the liquid chlorine 
falls and reduces the pressure. The effect of the fall in 
temperature, due to the latent heat of evaporation, can bfe 

* An effort is now being made to standardise cylinders of 150 lbs. capacity. 



96 



CHLORINATION OF WATER 



partially overcome by using a larger number of cylinders; 
in addition a source of external heat should be provided 
that will maintain the temperature of the cylinders at a 
minimum of 8o° F. This is a "sine qua non" for successful 
operation. The effect of the temperature upon the pressure 
in the cylinders is shown in Diagram VII. 

In practice it is found impossible to utilise all the gas 
contained in the containers; when the cylinders are almost 
empty the pressure necessary for the operation of the regulat- 

DIAGRAM VII 

CHLORINE GAS PRESSURES AT VARIOUS TEMPERATURES 

40 

30 
20. 













































90 

so 
70 
00 
50 
10 
30 
20 
10 

-10 
-20 






























































































































































































































































































































































































































































10 20 30 



40 50 60 70 80 90 100 110 120 130 140 150 160 170 
Pressure in Pounds per Square Inch 



ing device cannot be obtained and full cylinders must be 
attached. When sufficient heat is provided the weight of 
chlorine in the cylinder can be reduced to i-i| pounds before 
the tank pressure becomes too low. 

Liquid chlorine machines will operate, with ordinary 
care, for long periods. The various parts are made of such 
metals as experience has demonstrated to be best able to 
resist the corrosive action of the dry gas and the apparatus is 
designed to prevent the access of moisture which would other- 
wise produce corrosion and impede the flow of gas. Stop- 
pages are sometimes caused by brown deposits derived from 



LIQUID CHLORINE 



97 



impurities in the liquid chlorine. These are primarily due to 
variations in the graphite electrodes used in the electrolytic 
process for the manufacture of chlorine from salt. 

To convey the dry gas from the apparatus to the point of 
application, copper or iron pipes may be used; for aqueous 
solutions, flexible rubber hose must be employed. Chlorine 




' 'a* s > " r 
* C \ W «v Sf| M- € P*"'" ^ 





1 



Fig. 8. — Dunwoodie Chlorinating Plant Treating 400,000,000 Gallons Per Day 
for New York City. 



water is exceedingly active, chemically, and rapidly attacks 
all the common metals; ordinary galvanised iron pipe is 
eroded in a few days and should never be used. 

Liquid chlorine, for water disinfection, possesses several 
marked advantages over the ordinary bleach process. 

(1) The sterilising agent is practically 100 per cent pure, 



98 CHLORINATION OF WATER 

the only impurities being traces of carbon dioxide and air, 
and does not deteriorate on storage; it will, in fact, keep 
almost indefinitely. 

(2) Liquid chlorine practically eliminates all labour 
costs because of the simplicity of the apparatus and the 
concentrated form of the sterilising agent. The apparatus 
is so compact that all the cylinders and regulating apparatus 
required for delivering 200 pounds of gas per day can be 
placed in an area of about 50 square feet and it can conse- 
quently be almost invariably accommodated in locations 
where the trifling amount of attention required can be obtained 
without extra cost. 

(3) The sludge problem, inseparable from bleach instal- 
lations, is eliminated. 

(4) Regulation of the dosage is simpler and consequently 
usually more accurate. The dosing apparatus in bleach 
plants invariably tends to choke and demands regular atten- 
tion from intelligent operators; a similar tendency in liquid 
chlorine machines is easily detected and electrical devices 
can be installed to indicate automatically any changes in the 
flow. 

(5) The first cost is smaller. The cost of liquid chlorine 
machines varies from $400, for the small manual control 
types, to $1,200, for the automatic control types. The 
capital outlay is mainly determined by the number of 
machines and accessories required and not, within certain 
limits, by the capacity. One machine will deliver up to 200 
pounds of gas per day, an amount sufficient to treat 60,000,000 
U. S. A. gallons (50,000,000 Imp. gals.) at 0.40 p.p.m. of 
available chlorine. Unless duplicate machines are installed 
for the higher rates, the first cost is inversely proportional, 
though not directly so, to the volume of water treated. It 
is in all cases less than the first cost of a bleach plant of 
equal capacity, accuracy, and durability. 

(6) Liquid chlorine installations usually tend to produce 



LIQUID CHLORINE 99 

less complaints as to tastes and odours. This is probably 
due, not to any merit of the chlorine per se, but to a more 
accurate regulation of the dosage and efficient distribution 
of the chlorine in the treated water. The advantages ensuing 
from thorough admixture had only become partially appreci- 
ated before liquid chlorine machines were fully developed 
and they have been more fully utilised in the design of these 
later installations. 

Claims have also been made that liquid chlorine prevents 
"aftergrowths" but no evidence can be adduced in support 
of this statement. Aftergrowths have occurred at many 
places where this process is employed and in this respect it 
possesses no advantage over hypochlorite installations. 

It is also claimed that one pound of liquid chlorine is more 
efficient, as a germicide, than an equal weight of chlorine 
in the form of bleach. Jackson 5 has stated that i pound of 
chlorine is equal to 9 pounds of bleach; Kienle {loc. tit) 
that it was equal to 8 pounds of bleach, whilst Huy claimed 
to have obtained an efficiency ratio of 1 : 10 at Niagara Falls, 
N. Y. The conditions of the experiment were not comparable 
however, in the last mentioned ratio. Catlett, at Wilming- 
ton, N. C. (West 2 ) obtained a better bacterial reduction 
with 1 pound of liquid chlorine than with 6 pounds of bleach. 

The efficiency ratio of chlorine to bleach has been reported 
upon by West. 4 From 1910-1913 the mixed filter effluents 
of the Torresdale plant at Philadelphia were treated with 
bleach but in November, 19 13 the liquid chlorine process was 
substituted. On comparing the results obtained during the 
same months of the two periods it was found that, in general, 
1 pound of liquid chlorine gave a slightly higher percentage 
purification that 6-7 pounds of bleach. Similar results were 
obtained at the other Philadelphia plants. The figures 
published by West show that the hypochlorite solutions 
used were abnormally strong (3.6-10.4 per cent of available 
chlorine), a condition that would increase the difficulty of 



100 



CHLORINATION OF WATER 



extracting all the soluble hypochlorite. It was found indeed, 
that, under the most advantageous conditions, only 87 per 
cent of the available chlorine was extracted. The average 
chlorine content of the bleach used during 1912-1913 was 
36.1 per cent but the figures given would indicate that at 
least 1.5 per cent, a reduction of 4.6 per cent of the total, was 
lost during storage. It would seem not improbable that 
the total loss under average conditions was not less than 20 
per cent, which would reduce the efficiency ratio to 1 : 4.8-5.6. 
Hale 6 also made a comparison of the relative efficiency 
of liquid chlorine and hypochlorite of lime at New York, 
and the earlier results agreed with West's ratio of 1 : 6-7. 
An investigation showed that large quantities of chlorine 
were not extracted from the bleach and when this condition 
was rectified the total loss averaged only 4 per cent and 
the results obtained were equal to those given by the liquid 
chlorine machines. Hale's comparative figures are given in 
Table XXIII. 



TABLE ;XXIIL— COMPARISON OF LIQUID CHLORINE WITH 
EFFICIENT USE OF BLEACH— (Hale) 



Treatment. 


Water 
Treated. 


Number of 
Samples. 


Chlorine 
p.p.m. 


Reduction 
of B. coli. 


Bleach 

Liquid chlorine. . . . 


Croton 
Bronx 


84 
84 


O. 27-0.36 
O. 27-0.36 


93% 
93% 



Hale concluded that, when efficiently used, the ratio of 
chlorine to bleach required to produce equal bacterial puri- 
fication, approached 1:3, 

The results obtained by the author in Ottawa are similar 
to those of Hale. During the earlier period of the bleach 
treatment a dosage of 1.5 p.p.m. of available chlorine was 
required to obtain satisfactory purification but various 
improvements that were subsequently made enabled the 



LIQUID CHLORINE 101 

quantity to be reduced to 0.8 p.p.m. The same raw water 
usually requires 0.75 to 0.80 p.p.m. of liquid chlorine to 
obtain the same purification. The total losses in the Ottawa 
bleach plant averaged 6-8 per cent and based on these figures 
the efficiency ratio is approximately 1 : 3.5. 

Ratios as low as 1 : 3.5 can only be obtained by the super- 
vision of a chemist and this analytical control involves addi- 
tional expense that must be charged against the bleach proc- 
ess. No chemical analyses are necessary for the control 
of liquid chlorine plants. 

Disadvantages of Liquid Chlorine Plants. The main objec- 
tion to the use of liquid chlorine is that the slight leaks of 
gas occur occasionally and unless removed by forced ventila- 
tion may produce a concentration of chlorine that will injure 
the operators. 

Pettenkofer and Lehmann 7 found that 0.001-0.005 
per cent of chlorine in air . affected the respiratory organs ; 
0.04-0.06 per cent produced dangerous symptoms, whilst 
concentrations exceeding 0.06 per cent rapidly proved fatal. 

The danger of gas leakages can be eliminated by placing 
the apparatus in a small separate room provided with a fan 
and a ventilation duct. By the liberal use of giass in the 
construction of the room, the operation of the plant can be 
seen at all times without entering the chamber. 

A portion of the liquid chlorine apparatus is made of 
glass and is consequently easily fractured. Duplicates of 
the glass parts should be kept in stock to prevent inter- 
rupting the supply of gas; a duplicate machine is also advis- 
able in large installations. 

Cost of Treatment. Prior to the outbreak of war in 19 14, 
liquid chlorine sold at 10-11 cents per pound in small quan- 
tities and for 8-9 cents per pound in large shipments. In 
1917 the price was 18-20 cents per pound for small quantities 
and 15 cents upwards for large contracts. Canadian prices 
are 25 per cent higher. 



102 CHLORINATION OF WATER 

The amount of chlorine required for satisfactory disin- 
fection (see Chapter III) depends upon the nature of the 
water and the cost of treatment varies accordingly. In the 
majority of plants the cost varies from 25-90 cents per mil- 
lion gallons. 

Popularity of Process. Since 1913, when the first commer- 
cial liquid chlorine machines were used, the popularity of 
this process has increased in a most remarkable manner. 
In 1913 over 1,700 million gallons per day were treated with 
hypochlorite; in 191 5, 1,000 million gallons per day were 
treated with liquid chlorine and an approximately equal 
amount with hypochlorite; in January 1918, the amounts 
were 3,500 million gallons per day (liquid chlorine) and 500 
million gallons per day (hypochlorite). 

This wonderful development has been largely due to the 
intrinsic merits of the process and the reliability of the 
machines manufactured although it has been indirectly 
assisted by the excessive cost of hypochlorite during 191 5- 
1916. 

Liquid chlorine machines are being used for the purifica- 
tion of water on the Western Front of the European battle- 
field. The outfit is a mobile one and consists of a rapid sand 
filter, liquid chlorine apparatus, a small storage tank and 
solution tanks. Owing to the limited contact period available 
a large dosage of chlorine is employed and the excess after- 
wards removed by the addition of a solution of sodium thio- 
sulphate. 

Chlorine Water. Marshall 8 has proposed the use of 
chlorine water for the sterilisation of water for troops. The 
solution is contained in ampoules which are of two sizes, 
one for water carts and the other for water bottles of one 
quart capacity. 

The coefficient of solubility of chlorine, from io°-4i° C. 
is C = 3.0361 — 0.04196/+ 0.0001107/ 2 ; when /=io° C t can. 



LIQUID CHLORINE 103 

of water absorbs 2.58 c.cms. of chlorine or 8.2 m.gr., a quantity 
sufficient to give a concentration of 1 p.p.m. in 8 litres of 
water. Marshall has stated that, when pure materials are 
used, chlorine water is stable but the author is unable to 
confirm this. A saturated solution of chlorine in distilled 
water lost over 50 per cent of its available chlorine content 
when stored for five days in the dark at 70 F. The chlo- 
rine present as hypochlorous acid increased slightly but 
the quantity never exceeded very small proportions. Chlo- 
rine solutions decompose in accordance with the equation, 
Cl 2 +H 2 = 2HCl+0. 

Although chlorine water appears to be of little value 
because of its instability there appears to be no reason why 
chlorine hydrate should not be successfully employed. The 
hydrate was first prepared by Faraday 9 by passing chlorine 
into water surrounded by a freezing mixture. A thick yellow 
magma resulted from which the crystals of chlorine hydrate 
were separated by pressing between filter paper at o° C. 
The hydrate prepared by Faraday was found to have the 
composition represented by the formula CT5H2O but later 
investigators have shown that more concentrated hydrates 
can be prepared. Roozeboom 10 prepared a hydrate repre- 
sented by the formula CI • 4H2O and Forcrand one containing 
only 3§ molecules of water (CVyH^O). Chlorine hydrate 
separates into chlorine gas and chlorine water at 9. 6° C. 
in open vessels and at 28. 7 C. in closed vessels. Pedler 12 
has shown that when the ratio of CI2 : H2O is 1 : 64 or greater, 
the mixture of chlorine hydrate and water exhibits great 
stability and can be exposed to tropical sunlight for several 
months without decomposition. 

CI2 -641^20 contains 5.8 per cent of chlorine and about 
8. c.cms. would be required to give a concentration of 1 p.p.m. 
in no Imp. gallons of water, the usual capacity of a military 
water cart. 



104 CHLORINATION OF WATER 



BIBLIOGRAPHY 

(i) Nesfield. Public Health, 1903, 15, 601. 

(2) Darnall. J. Amer. Pub. Health Assoc, 191 1, I, 713. 

(3) Kienle. Proc. Amer. Waterworks Assoc, 1913, 274. 

(4) West. J. Amer. Waterworks Assoc, 1914, 1, 400-446. 

(5) Jackson. Proc. Amer. Waterworks Assoc, 1913. 

(6) Hale. Proc. N. J. San. Assoc, 19 14. 

(7) Pettenkofer and Lehmann. Munich Acad., 1887. 

(8) Marshall. Conv. Amer. Elect. Chem. Soc, 191 7. ■ Eng. and Contr., 

1918, 49, 40. 

(9) Faraday. Q. J. S., 15, 71. 

(10) Roozeboom. Rec Trav. Chim., 1885, 3, 50. 

(11) Forcrand. Comp. rend., 1902, 134, 991. 

(12) Pedler. J. C. S., 1890, 83, 613. 



CHAPTER VIII 
ELECTROLYTIC HYPOCHLORITES AND CHLORINE 

Since 1889 when Webster first proposed the use of elec- 
trolysed sea-water as a disinfectant, various attempts have 
been made to introduce electrolytic hypochlorites for the 
bactericidal treatment of water and sewage. Two of these 
preparations were named Hermite fluid, and electrozone 
(c.f. page 5). Sodium hypochlorite, made by passing 
chlorine into solutions of caustic soda, or by the decom- 
position of bleach by sodium carbonate, has also been used 
and preparations of this character have been sold under such 
names as Eau de Javelle, Labarraque solution, chloros, and 
chlorozone. These solutions contain mixtures of sodium 
hypochlorite and sodium chloride together with some free 
alkali. Chlorozone was the name given by Count Dienheim- 
Brochoki to a number of preparations patented in 1876 and 
subsequently down to 1885. They were produced by passing 
air and chlorine into solutions of caustic soda. Lunge and 
Landolt 1 have shown that the air introduced is without 
effect and that the advantages claimed for chlorozone are 
illusory. 

The earliest electrolytic installation on this continent was 
operated at Brewster, N. Y., in 1893 and since that date 
several plants have been erected where local conditions con- 
duced to economical operation. 

When a uni-directional current of electricity is passed 
through a solution of sodium chloride, the salt is dissociated 
and the components liberated. NaCl = Na-|-Cl. If the ele- 

105 



106 CHLORINATION OF WATER 

ments are not separated, the chlorine combines with the 
sodium hydrate, formed by the action of the sodium on the 
water, to form sodium hypochlorite. The equations 
2 Na + 2H 2 = 2NaOH+H2,and2NaOH+Cl2 = NaOCl+NaCl 
+H2O show that only one-half of the chlorine produced is 
found as hypochlorite; the other half reforming sodium 
chloride. 

Several types of electrolysers have been used for the pro- 
duction of hypochlorites and chlorine but only two are suitable 
for water-works purposes: in one, the cathodic and anodic 
products recombine in the main body of the electrolyte ; in the 
other, the diaphragm process, they are separated as removed 
and the final products are chlorine gas and a solution con- 
taining caustic soda and some undecomposed salt. 

Until a few years ago the non-diaphragm process was the 
only one used for water treatment and it will consequently 
be discussed first. 

Non-diaphragm Process. The theoretical voltage required 
for the decomposition of sodium chloride is 2.3 but when the 
products recombine in the electrolyte, side reactions occur 
which increase the minimum voltage to 3.54. On this basis 
one kilowatt hour gives 272 ampere hours and as one ampere 
hour is theoretically capable of producing 1.33 grams of 
chlorine, 1.21 kilowatt hours are necessary for the pro- 
duction of 1 pound of chlorine by the decomposition of 1.65 
pounds of salt. 

Charles Watt (1851) discovered this process and was the 
first to recognize the necessary conditions which are (1) 
insoluble electrodes, (2) low temperature of electrolyte, and 
(3) rapid circulation of electrolyte from the cathode to the 
anode. The control of the temperature is very important, 
for as it increases, side reactions occur with the formation 
of chlorates, and the efficiency is decreased. 

The non-diaphragm cells used in Europe (Haas and Oet- 
tel, Kellner, Hermite, Vogelsand, and Mather and Piatt) 



ELECTROLYTIC HYPOCHLORITES AND CHLORINE 107 

have been described by Kershaw. 2 In the Haas and Oettel 
electrolyser the electrodes are composed of carbon but in the 
other types at least one electrode is made from platinum or a 
platinum alloy. The Dayton electrolyser, which is the cell 
most familiar in North America, is shown in Fig. 9. 

The outer cell is made of soapstone and is approximately 




¥f¥f§*$fw°§jV'£ 




r- ;§ 



it, ■ 



Fig. o. — Dayton Electrolytic Cell. 

of four pieces of Atcheson graphite connected together by 
screws and metal strips to which is attached a clamp for 
connecting electrical terminals. Circulation of the brine is 
produced by glass baffle plates and secondary electrodes 
placed one inch apart between the main electrodes. The 
cell is intended to be used at no- volts pressure but by wiring 
two cells in series a 2 20- volt circuit may be employed. An 
inlet and outlet are provided at each end of the tank to permit 
the direction of the flow to be periodically reversed for the 



108 



CHLORINATION OF WATER 



purpose of removing the lime deposit -from the graphite 
plates. 

The salt solution is prepared in wooden tanks from coarse 
clean salt (ground rock salt is unsuitable), containing as little 
iron as possible, in the proportion of 50 pounds to 100 gallons 
of water. After passing through a gravel or other suitable 
filter the brine solution is carried by brass pipes to the elec- 
trolyser. The rate of flow is adjusted to the temperature 
of the hypochlorite solution leaving the cell but under normal 
conditions it is stated that the cell described will pass 40 
gallons per hour with a consumption of 70 amperes and pro- 
duce 2% pounds of chlorine per hour. This is equal to 8 
pounds of salt and 3.08 kilowatt hours per pound of chlorine. 
After the cells have been operated for several months the 
efficiency usually falls and 10-11 pounds of salt and 3.5-3.7 
kilowatt hours are required for the production of one pound 
of chlorine. The concentration of the hypochlorite solution 
is usually about 6 grams per litre. 

Rickard 3 stated that by cooling the Dayton cell with ice 
1 pound of chlorine could be produced from 2.65 kilowatt 
hours and 6.9 pounds of sodium chloride; without cooling 
the figures were 3.62 kilowatt hours and 7.2 pounds of salt. 
Based on the figures that have been obtained from mature 
cells, the efficiency of the Dayton cell as compared with those 
described by Kershaw is as follows: 



Type of Cell. 


Salt. Power. 
Per Pound of Available Chlorine. 


Pounds. 


Per Cent 
Consumed. 


Kilowatt 
Hours. 


Efficiency 
Per Cent. 


Haas and Oettel 

Kellner 

Hermite 

Mather and Piatt. . . . 

Dayton 

Theoretical 


10. 7 

7-5 

11. 2 

IO.O 
I.65 


» 15-4 
22.0 

14-5 

16. 5 
100. 


3-8 

2-75 
2.87 

2-75 
3-6 
1 . 21 


31-9 
43-9 
42. 2 

43-9 

33-6 

100. 



ELECTROLYTIC HYPOCHLORITES AND CHLORINE 109 



The cost of production depends upon local conditions: if 
alternating current is available at $30 per horse-power per 
annum, and low-grade salt can be obtained for $5 per ton 
the cost of 1 pound of chlorine would be 



Type of Cell. 


Cost (Cents, 


Per Pound 
Chlorine. 


df Available 




Salt. 


Current. 


Total. 


Haas and Oettel 


2.67 
1.87 
2.80 
2.50 


I.97 
i-43 
i-49 
1.92 


4.64 

3-3° 
4.29 
4.42 


Kellner 

Hermite 


Dayton 





The electrical and chemical efficiencies of the Haas and 
Oettel and Dayton cells, which contain carbon electrodes, 
are smaller than those containing platinum electrodes but 
for water sterilisation the carbon cells have been found to be 
more suitable. To prevent the action of magnesium salts 
on the platinum electrodes it is necessary to use a higher 
grade of salt or to provide means of purification. Because 
of the absence of a base and the presence of chlorides, elec- 
trolytic hypochlorite cannot be stored for more than a few 
hours without appreciable loss of titre. Unless used for the 
treatment of the effluent of a filter plant operated at a fairly 
constant rate a small storage tank is necessary to compensate 
for the irregular demand and to provide the head required 
by orifice feed boxes. Small variations can be made by regu- 
lating the flow through the cells but large ones are not com- 
patible with efficiency, which is the highest under a con- 
stant load. 

Claims have been made that electrolytic hypochlorite 
is more efficient as a germicide than bleach when compared 
on the basis of their available chlorine content but no evidence 
of it has been produced. Bleach contains an excess of base, 
which retards the germicidal action, and electrolytic hypo- 



110 



CHLORINATION OF WATER 



chlorite contains an excess of sodium chloride, which acceler- 
ates it (Race 4 ) but the ultimate effect is the same with both. 
This is shown in Table XXIV. 

TABLE XXIV.*— COMPARISON OF BLEACH WITH ELECTROLYTIC 
HYPOCHLORITE 





ii 
Bleach. 1 Electrolytic Hypochlorite. 


Contact Period. 


Available Chlorine. Parts Per Million. 




0.4 


0.6 


0.4 


0.6 


Nil 


182 

130 

66 

3 



10 

1 




120 
60 

1 





10 minutes 

i hour 

2 hours 

3^ hours 


8 






* Results are B. coli per 10 cans. 

Electrolytic hypochlorite has a greater germicidal velocity 
than bleach but the difference is so small as to be of no prac- 
tical importance. Rabs 5 experimented with various hypo- 
chlorites but was unable to find any appreciable differences 
in their germicidal action. 

If electrical power can be obtained at a very low cost, 
or if the cost is merely nominal, as it is when there is an 
appreciable difference between the normal consumption 
and the peak load upon which the rate is based, the electro- 
lytic hypochlorite method offers some advantages but in 
the great majority of plants it cannot economically compete 
with bleach. The instability of the liquor and cell troubles 
have also prevented the process being generally utilised. 
Baltimore and Cincinnati experimented with this method 
but did not adopt it. Winslow 6 has reported that, owing to 
the difficulty in obtaining bleach since the outbreak of war, 
Petrograd has used electrolytic hypochlorite made from salt. 

Diaphragm Process. The various types of diaphragm 
cells that have been commercially operated are of two vari- 



ELECTROLYTIC HYPOCHLORITES AND CHLORINE 111 

ties: (i) cells with submerged diaphragms and (2) cells in 
which the electrolyte comes in contact with one face only 
of an unsubmerged diaphragm. 

The Le Sueur, Gibbs, Crocker, Billiter-Siemens, Nelson, 
and Hargreaves-Bird cells are of the submerged diaphragm 
variety. The Nelson cell has been operated for some time 
at the filtration plant at Little Falls, N. J. The cells are fed 
with brine solution previously purified by the addition of soda 
ash and have given fairly successful results although the 
cost of maintenance is comparatively high. Tolman 7 has 
reported that several towns in West Virginia use a bleach 
solution prepared by absorbing chlorine, manufactured by 
the Hargreaves-Bird process, in lime water; the solution 
contains about 1.95 per cent of available chlorine. 

The diaphragms in both the submerged and unsubmerged 
types are usually constructed either with asbestos paper or 
cloth, placed in such a manner as to divide the cells into two 
separate compartments: the anodic, into which the brine is 
fed and where the chlorine is produced; and the cathodic, 
where caustic soda is formed. 

By maintaining the liquor in the anodic compartment 
at a higher elevation than in the cathodic one, the direction 
of flow is towards the latter, but owing to osmosis and diffu- 
sion the separation is not complete and a portion of the 
caustic soda passes the diaphragm and produces hypochlorite 
with a consequent loss of efficiency and rapid deterioration 
of the anodes. With the exception of the Billiter-Siemens 
cell, the submerged diaphragm cells operate at not more than 
85 per cent efficiency and the cost of maintenance is usually 
high. 

In the non-submerged diaphragm types the invasion 
of the anodic compartment by caustic is much reduced and 
the efficiency and life increased. 

An electrolyser of the non-submerged diaphragm type 
is the Allen-Moore cell which has been adopted by the Mon- 



112 



CHLORINATION OF WATER 



treal Water and Power Co. This has been described by 
Pitcher and Meadows. 8 The general lay-out of the installa- 
tion is shown in Fig. 10, and the essential features are: a 
salt storage bin having a capacity of 40 tons; the brine satu- 
rating and purifying apparatus; duplicate 15 horse-power 
motor-generator sets; four chlorine cells; and the silver 
ejectors and distributing lines for carrying the chlorine solu- 
tion to the point of application. 




Fig. 10.— Brine Saturating and Purifying Equipment. 



The brine solution, which is prepared by passing water 
through the saturators previously filled with salt, is delivered 
to the two concrete reaction tanks where an amount of soda 
ash and caustic liquor sufficient to combine with the calcium 
and magnesium salts is added, and the mixture filtered 
through sand and stored in the purified brine tanks. To 
prevent the formation of hypochlorites by the interaction 
of chlorine and alkali, the alkalinity of the liquor is deter- 



ELECTROLYTIC HYPOCHLORITES AND CHLORINE 113 

mined and sufficient hydrochloric acid added to ensure an 
acidity of o.oi per cent. The acid brine is delivered at one 
end of the four cells (Fig. n) each of which is 7 feet long and 
2o| inches wide and consumes 600 amperes at 3.3 volts. 
The cell box is built of concrete and is provided with a per- 
forated wrought iron cathode box and graphite anode plates 
which are separated by an unsubmerged asbestos paper 
diaphragm. 

Each cell has a capacity of 32 pounds of chlorine per 
day and the gas flow is determined by measuring the volume 
of caustic soda produced in a given period of time and calcu- 



Carbon 
anode Chlorine gas 

1 ° Ut fijff==f 



Brine influent 
regulating &, valve 




Fig. 11. — Sections of Allen-Moore Cell. 



lating the weight from the volume and concentration as 
determined by titration with standard acid; each gram of 
NaOH is equal to 0.88 gram of chlorine. The efficiency 
of the cell is obtained by dividing the number of grams of 
chlorine produced per hour by the product of the current 
volume (in amperes) and the factor 1.33, the theoretical 
production of chlorine for one ampere hour. The average 
efficiency of the Montreal cells was found to be 93 per cent. 
The installation comprises four cells, one being held in reserve, 
and the annual cost of producing 90 pounds of chlorine per 
day is given as $2,500. The details are: 



114 CHLORINATION OF WATER 

Salt at $8.00 per ton, delivered $500.00 

Power, 15 H.P., at $30.00 flat rate 450.00 

Labour and superintendence 500 . 00 

Interest at 6 per cent on capital cost 300 . 00 

Depreciation, 15 per cent 750 . 00 



f>2,500.00 



cost per pound of chlorine = 7.6 cents. 

The diaphragm cells, like the non-diaphragm ones, operate 
most efficiently under a constant load; they are consequently 
suitable for treating the effluent of filter plants. 

Where very cheap electrical power can be obtained, the 
cost per pound of available chlorine is less for the electrolytic 
method just described than for liquid chlorine or chlorine 
obtained from bleach; but this condition obtains in very few 
places. Mr. J. A. Meadows has suggested to the author 
that the cost could be reduced by converting the chlorine 
gas into hypochlorite and then adding dilute ammonia as 
in the chloramine process (vide page 115). The caustic 
liquor, usually run to waste from the cathodic compartment, 
could be delivered into a feed box from which it would be 
drawn off by the water injector used for dissolving the chlorine 
gas. 

BIBLIOGRAPHY 

(1) Lunge and Landoll. Jour. Soc. Dyers and Colourists, Nov. 25, 1885. 

(2) Kershaw. Jour. Soc. Chem. Ind., 1912, 31, 54. 

(3) Rickard. Quar. Bull. Ohio Board of Health, Oct.-Dec., 1904. 

(4) Race. Jour. Amer. Waterworks Assoc, 1918, 5, 63. 

(5) Rabs. Hygiensche Rundschau, 1901, 11. 

(6) Winslow. Public Health Rpts. U. S. P. H. S., 191 7, 32, 2202. 

(7) Tolman. Jour. Amer. Waterworks Assoc, 1917, 4, 337. 

(8) Pitcher and Meadows. Jour. Amer. Waterworks Assoc, 191 7, 4, 337. 



CHAPTER IX 
CHLORAMINE 

Chloramine (NH2CI), a chemical compound in which 
one of the hydrogen atoms of ammonia has been replaced 
by chlorine, was discovered by Raschig 1 in 1907. Chlora- 
mine was prepared by cooling dilute solutions of bleach 
and ammonia and adding the latter to the former contained 
in a flask surrounded by a freezing mixture. The propor- 
tions were as the equivalent weights of anhydrous ammonia 
and available chlorine (approximately two parts by weight 
of chlorine to one part by weight of ammonia). After gas 
evolution had ceased the mixture was saturated with zinc 
chloride and the magma distilled under reduced pressure. 
The distillate was a dilute solution of comparatively pure 
chloramine. 

The first to notice the effect of ammonia on the germi- 
cidal value of hypochlorites was S. Rideal 2 who noted that 
during the chlorination of sewage, the first rapid consumption 
of chlorine was succeeded by a slower action which continued 
for days in some instances, and was accompanied by 
a germicidal action after free chlorine or hypochlorite had 
disappeared. Rideal stated that: "It became evident that 
chlorine, in supplement to its oxidising action, which had been 
exhausted, was acting by substitution for hydrogen in am- 
monia and organic compounds, yielding products more or 
less germicidal." On investigating the effect of ammonia 
on hypochlorite it was found that the addition of an equivalent 
of ammonia to electrolytic hypochlorite increased the car- 

115 



116 CHLORINATION OF WATER 

bolic acid coefficient of 2.18, for one per cent available chlorine, 
to 6.36 (nearly three times the value). Further experimental 
work showed that the increase was due to the formation of 
chloramine. 

The author, in 19 15, during a series of experiments on 
the relative germicidal action of hypochlorites, attempted 
to prepare the ammonium salt by double decomposition of 
bleach and ammonium oxalate solutions. 

Ca(OCl)2+(NH 4 ) 3 C204 = CaC 2 4 +2NH 4 OCl. 

The velocity of the germicidal action of the solution was 
found to be about ten times greater than the germicidal 
velocities of other hypochlorites of equal concentrations, 
(Race 3 ), and from a consideration of the chemical formula 
of ammonium hypochlorite it appeared probable that it would 
be very unstable and decompose into chloramine, which 
Rideal had previously shown to have an abnormal germicidal 
action, and water. NH 4 0C1 = NH 2 C1+H20. After these 
results have been confirmed, the effect of adding ammonia 
to bleach solution was tried and it was found that 0.20 p.p.m. 
of available chlorine and 0.10 p.p.m. of ammonia produced 
equally good results as 0.60 p.p.m. of chlorine only. Similar 
results were obtained on the addition of ammonia to elec- 
trolytic hypochlorite. 

Experiments made with a view to determining the most 
efficient ratios of ammonia gave very surprising results: 
chlorine to ammonia ratios (by weight) between 8 : 1 and 
1 : 2 gave approximately the same germicidal velocity. 3 
The action of the ammonia on the oxidising power of bleach, 
as measured by the indigo test, was also found to be dispro- 
portionate to the amount added. 

The oxidising action of various mixtures of bleach and 
ammonia as measured by the rate of absorption of the avail- 
able by the organic matter in the Ottawa River water is 
shown in Table XXV. 



CHLORAMINE 117 

TABLE XXV.— RATE OF ABSORPTION OF AVAILABLE CHLORINE 



_ . Chlorine , „ . , , 

Ratio -. — by Weight. 

Ammonia 


Percentage of Original Found After 


io Mins. 


4 Hours. 


20 Hours. 


Infinity (ammonia absent) 

8 : i 


66.8 
83.2 
97.2 

98-3 
99.8 


40.O 

77-8 
94-7 
96.5 
98.2 


2S-I 
67-3 
88.5 
92.8 
96.2 









The 8 : 1 ratio caused a marked reduction in the rate of 
absorption of the chlorine whilst a 4 : 1 ratio was almost as 
active as the ratios containing more ammonia. 

At the time when the abnormal results were obtained 
with ammonium hypochlorite and mixtures of bleach and 
ammonia, the phenomenon appeared to be of scientific interest 
only and especially so as Rideal had attributed the obnoxious 
tastes and odours, sometimes produced by chlorination, 
to the formation of chlor amines. During the winter of 
1915-1916 the price of bleach, however, advanced to extra- 
ordinary heights and the author then determined to try out 
the process on a practical scale for the purification of water. 
A subsidiary plant pumping about 200,000 Imperial gallons 
per day (240,000 U. S. A. gallons) was found to be available 
for this purpose and the chloramine process was substituted 
for the bleach method previously in operation. The process 
was commenced by the addition of pure ammonia fort, in 
the amount required to give a chlorine to ammonia ratio of 
2:1, to the bleach solutions in the barrels. The results 
were not in accordance with those obtained in the laboratory 
and it was found that the samples of bleach solutions received 
for analysis were far below the strength calculated from the 
amount of dry bleach used. This experience was repeated 
on subsequent days and the deficiency was found to increase 
on increasing the ammonia dosage. Solutions of similar 



Il8 CHLORINATION OF WATER 

concentration were then used in the laboratory with similar 
losses, and it was observed that on the addition of ammonia a 
copious evolution of gas occurred. An investigation showed 
that the ammonia and bleach must be mixed as dilute solu- 
tions and prolonged contact avoided {vide p. 127). Altera- 
tions were accordingly made in the plant and the bleach and 
ammonia were prepared as dilute solutions in separate vessels 
and allowed to mix for only a few seconds before delivery to 
the suction of the pumps. This method of application was 
instantaneously successful and results equal to those obtained 
in the laboratory were at once secured. The dosage was 
reduced until the bacteriological results were adversely 
affected and continued at values slightly in excess of this 
figure (0.15 p.p.m.) for a short period to prove that the 
process was reliable. 

From a consideration of the work of Raschig and 
Rideal, it appeared that the most efficient proportions of 
available chlorine and ammonia would be two parts by weight 
of the former to one part of the latter and this ratio was 
maintained during the run on the experimental plant. Lower 
ratios of chlorine to ammonia were contra-indicated by the 
laboratory experiments, which showed that the efficiency 
was not increased thereby whilst higher ratios were left for 
future consideration. 

The results obtained on the experimental plant, together 
with those obtained on the main plant, where 24 million 
gallons per day were treated with bleach only, are given in 
Tables XXVI, XXVII and XXVIII. The two periods given 
represent the spring flood condition and that immediately 
preceding it; these are respectively the worst and best water 
periods. The results in both cases are from samples examined 
approximately two hours after the application of the 
chemicals." 

The cost data were calculated on the current New York 
prices of bleach and ammonia. 



CHLORAMINE 



119 



TABLE XXVI.— COMPARISON OF HYPOCHLORITE AND CHLORA- 
MINE TREATMENT 

Bacteriological Results 









Treated with 


Treated with Hypo- 




Raw Water. 


Hypochlorite 


chlorite and 








Alone. 


Ammonia. 








Bacteria 






Bacteria 














per cubic 


O 




per cubic 


Q 








centimeter. 





centime- 


O 





centime- 





c 


ft 


1916 






ter. 




h.H 


ter. 




c.y 






<L» 




<a 


u Zl 




0) 


C r3 


-t_> 






















O, 


S 






















X 


ft 




H £ 






■do 


■do 


■d 
a 


iJ ft 


£0 
■00 


£0 

•do 


13 


.2 a 

.a to 

'St! 


is 

c 
— 

11 




St* 




8 " 
y 




&* 





'3 is 




a« 








< 


< 


cq 


< 


<J 


cq 


<3 


< 


<J 


uq 


<J 


<3 


Mar. 15-31 


44 


238 


35-7 


4 


12 


<o.i4 


o.go 


4 


12 


0.14 


O. 22 


0. 11 


April 1-19 


3,099 


14,408 


i95 5 


3 2 


56 


0.50 


1. 10 


33 


246 


0.74 


O.25 


0.13 



TABLE XXVII 

Percentage Reduction 





Hypochlorite Alone. 


Hypochlorite and Ammonia. 




Bacteria per 
cubic centi- 
meter 


B. coli 

Index 

per 100 

cubic 

centi- 
meters. 


Avail- 
able 
Chlo- 
rine 
Parts 
per 
Million. 


Bacteria per 
cubic centi- 
meter 


B. coli 
Index 
per 100 
cubic 
centi- 
meters. 


Avail- 
able 
Chlo- 




Agar 1 
Day at 
37° C. 


Agar 3 
Days at 

20° C. 


Agar 1 
day at 
37° C. 


Agar 3 
Davs at 
20° C. 


rine 

Parts 

per 

Million. 


Mar. 15-31 

April 1-19 


90.9 
98.9 


95-8 
99.6 


99-9 + 
99-7 


0.90 
I . 10 


90.0 
98.3 


95 -° 
98.9 


99-7 
99.6 


O. 22 
O.25 



TABLE XXVIII 

Cost Per Million Imperial Gallons * 




Hypochlorite 
and ammonia.' 



Mar. 15-31. 
April 



Jo. 46 
o.54 



♦Calculated en Bleach at S3. 80 per 100 pounds and aqua ammonia (26° Be.) at 
SJi cents per pound. 



120 



CHLORINATION OF WATER 



The results were so satisfactory that the author recom- 
mended the adoption of the process on the main chlorinating 
plant but owing to conditions imposed by the Provincial 
Board of Health the process was not operated until February, 
1917. 

In place of ammonia fort, aqua ammonia (26 Be.), con- 
taining approximately 29 per cent of anhydrous ammonia, 
was used. The material wa^ first examined by the presence 
of such noxious substance as cyanides and found to be very 
satisfactory. 




Fig. 12. — Sketch of Ottawa Chloramine Plant. 



The general design of the plant is shown in Fig. 12. 
The bleach is mixed in tank A as a solution containing 0.3 
to 0.6 per cent of available chlorine and delivered to tanks 
B and D, each of which has a twenty-four-hour storage capa- 
city. The ammonia solution is mixed and stored in tank B 
and contains 0.3-0.5 per cent of anhydrous ammonia. The 
two solutions are run off into boxes E and F which maintain 
a constant head on valves V and V controlling the head on 
the orifices. Both orifices discharge into a common feed 



CHLORAMINE 



121 



box G from which the mixture is carried by the water injector 
J through one of duplicate feed pipes and discharged into 
the suction well through a perforated pipe. 

As tank B was previously used as a bleach storage tank, 
the change from hypochlorite alone to chloramine necessitated 
very little expense. 

The treatment was commenced by gradually increasing 
the quantity of ammonia, until a dosage of 0.12 p.p.m. was 
reached, and constantly increasing the dosage of bleach, 
which was formerly 0.93 p.p.m. of available chlorine. Owing 
to the restrictions imposed by the Provincial authorities 
it has not been possible to maintain a dosage as low as that 
indicated as sufficient by the experimental plants results, 
but some interesting data have been obtained. Table XXIX 
shows the results obtained from February to October, 191 7, 
from the chloramine treatment at Ottawa and also those 
obtained with liquid chlorine at Hull where the same raw 
water is treated with 0.7-0.8 p.p.m. of chlorine. 

TABLE XXIX.— CHLORAMINE RESULTS AT OTTAWA 





B. coli 
Per 100 c.cms. 


Turbidity 


Colour. 


Dosage p.p.m. 




Hull 
B. coli 


1917 


Raw. 

Water. 


Tap 

Water. 


Chlorine. 


Ammonia 


Per 100 
c.cms. 


Feb 

Mar. 1-18 
Mar. 1-3 1 
April 
May 

June 

July 

Aug 

Sept 

Oct 


268 
250 

643 

5228 

162 

114 

237 

165 

55 

31 


O.88 

O.96 

0.43 

0.34 

<o.o8 

<o.o8 

0.08 

0.08 

<o.o8 

o-i5 


3 
4 
4 
3i 
3 
3 
5 
4 
6 

5 


40 
40 
40 
32 
39 
41 
41 
42 
42 
42 


°-57 
0.32 
0.47 
0.56 
0.52 
0-5I 
0-5I 
0.51 
0.50 
0.42 


O.05 
O. II 
O.14 
O.IO 

0.08 
O.08 
O.08 

O.IO 

0.09 

0.08 


i 

1 


[4-4 
28.0 

C5-2 

I.I 


Average.. 


211 


0.22 


7 


40 


o-5i 


0.09 







122 CHLORINATION OF WATER 

At the height of the spring floods the raw water con- 
tained 80 p.p.m. of turbidity and over 500 B. coli per c.cm. 
but 0.6 p.p.m. of chlorine and 0.13 p.p.m. of ammonia reduced 
the B. coli index in the tap samples to 2.5 per 100 c.cms. ; 
samples taken in Hull on the same day (treated with 0.7-0.8 
p.p.m. of liquid chlorine) gave a B. coli index of 26.7. Previous 
experiences in Ottawa has shown that a dosage of approxi- 
mately 1.5 p.p.m. of available chlorine is required to reduce 
the B. coli index to 2.0 per 100 c.cms. under similar physical 
and bacteriological conditions. 

During the period of nine months covered by the results 
in Table XXIX, only five cases of typhoid fever were reported 
in which the evidence did not clearly indicate that the infec- 
tion had occurred outside the city. The reduction in the 
bleach consumed during the same period effected a saving of 
$3,200. 

During one period of operation the hypochlorite dosage 
was gradually reduced to ascertain what factor of safety 
was maintained with a dosage of 0.5 p.p.m. of available 
chlorine and 0.06-0.08 p.p.m. of ammonia. The results are 
shown in Diagram VIII. The percentage of samples of treated 
water showing B. coli in 50 c.cms. was calculated from the 
results of the examination of 4-7 samples daily. 

The results showed that it was possible to reduce the 
chlorine dosage to 0.25 p.p.m. with 0.06 p.p.m. of ammonia 
without adversely affecting the bacteriological purity of the 
tap supply and fully confirmed the experimental results 
previously obtained. 

The lowest ratio of available chlorine to ammonia used 
during this test was approximately 4:1. This is the ratio 
indicated by a consideration of the theory of the reactions 
and not 2 : 1 as was formerly stated (Race 4 ). If bleach is 
represented as Ca (00)2, the equation 

Ca(OCl)2 + 2NH 3 = 2NH 2 Cl+Ca(OH)2 



CHLORAMINE 



123 



would indicate a ratio of 2:1; but only one molecule of 
Ca(OCl)2 is produced from two molecules of bleach and the 
theoretical ratio is therefore 4 : 1 (142 : 34), 

2CaOCl 2 = CaCl 2 +Ca(OCl) 2 and Ca(OCl) 2 + 2 NH 3 

Cl=i42 34 

= 2NH 2 Cl+Ca(OH) 2 . 

The chlorine to ammonia ratio is very important because 
of its influence on the economics of the process {vide p. 124). 

















DIAGRAM VIII 

CHLORAMINE TREATMENT, 


OTTAWA 
















100 

90 


Raw \ 


Vater- 


-r 


srcentage c 


f samples 


COD 


tail 


inf 


B. 


t'ol 


m 1 c.cra. 
























































































































































































































































50 
10 
































































































































































































































































































Trt 


ited- 


Wat 


























































pier 








































20 

10 


























































































































































































































0.50 
0.15 
0.10 
0.35 
0.30 
0.25 
0.20 
0.15 
0.075 
























































/ 






































































Ai 


ail 


ll.lt 


ch 


ori 


ae— 


pa 


tS] 


er 


nill 


ion 




























































































































































































































































































































Ammo 


lia- 


-pa 


rlK 


I 1 


mi 


]iui 






























0.05 
0.036 


























1 



































































































































3 1 6 6 7 8 9 10 11 12 13 11 15 16 17 18 19 20 21 22 23 24 25 2fi 27 28 29 30 

Date 

All the laboratory and works results that have been 
obtained in Ottawa indicate the importance of an adequate 
contact period. The superiority of chloramine over other 
processes is due to the non-absorption of the germicidal agent 
and to obtain the same degree of efficiency the contact period 
must be increased as the concentration is decreased. For 
this reason the best results will be obtained by chlorinating 
at the entrance to reservoirs or under other conditions that 
will ensure several hours contact. At Ottawa the capacity 



124 CHLORINATION OF WATER 

of the pipes connecting the pumping station (point of chlori- 
nation) and the distribution mains provides a contact period 
of one and a quarter hours but even better results would be 
obtained if the contact period were increased. 

The general results obtained during the use of chloramine 
at Ottawa in 19 17 have shown that the aftergrowths noted 
during the use of hypochlorite (see p. 56) have been entirely 
eliminated and that the B. coli content of the tap samples 
from outlying districts has been invariably less than that of 
samples taken from taps near to the point of application of 
the chloramine. At Denver, Col., where the chloramine 
process has also been used, similar results were obtained 5 : 
four days after the initiation of the chloramine treatment 
the aftergrowth count on gelatine of the Capitol Hill reservoir 
dropped from 15,000 to 10 per c.cm. The hypochlorite dos- 
age was cut from 0.26-0.13 p.p.m. of available chlorine and 
0.065 P-P- m - °f ammonia added. 

Economics of the Chloramine Process. The chloramine 
process was introduced at Ottawa for the purpose of obtaining 
relief from the effect of the high price of bleach caused by the 
cessation of imports from Europe in 191 5. The results 
obtained with the experimental plant indicated that, cal- 
culated on the prices current at the beginning of 19 17, appre- 
ciable economies could be made. Although the reduction 
in the chlorine dosage has not been as great as was anticipated, 
due to the restrictions previously mentioned, the cost of 
sterilising chemicals in 191 7 was $3,200 less than the cost of 
straight hypochlorite treatment. 

During the latter part of 1917 the relative cost of bleach 
and ammonia changed (see Diagram IX). 

When calculated on the New York prices for January, 
1918, the cost of chloramine treatment in the -United States 
would be greater than hypochlorite alone unless a large 
reduction in the dosage could be secured by very long contact 
periods. This condition is only temporary, however, and 



CHLORAMINE 



125 



the price of ammonia will probably gradually decline as the 
plants for fixation of atmospheric nitrogen commence opera- 
tions and reduce the demand for the ammonia produced from 
ammoniacal gas liquor. 

In Canada, the market conditions are still (191 8) favour- 
able to the chloramine process: bleach is 25 per cent higher 
than the U. S. A. product and ammonia can be obtained for 
one-half the New York prices. 



DIAGRAM IX 

BLEACH AND AMMONIA PRICES 



20 



BIS 



110 

















































































/ 


20 












































































1 
1 
1 




/ 






































\i 


le 


ac 


h 




























is 




1 






































/ 




















nr 


H 


n 


a 


!6 


'I 


i. 






/ 












5 




V 




--^ 




















'A 


11 


no 


nla 


ie 


°i 


',. 




































































.0 


.4 +— — 1915 — 


« 1 


Jl 


3 


* 191-7 * 


<1 


J18 



Advantages of the Chloramine Process. Although the 
market conditions may, in some instances, be unfavourable 
to the chloramine process, the method possesses certain 
advantages that more than offset- a slight possible increase 
in the cost of materials. The taste and odour of chloramine 
is even more pungent than that of chlorine but since the intro- 
duction of the process in Ottawa no complaints have been 



126 CHLORINATION OF WATER 

received. Owing to the reduced dosage, slight proportional 
fluctuations in the dosage do not produce the same variations 
in the amount of free chlorine which is the usual cause of 
complaints. A public announcement that the amount of 
hypochlorite has been reduced also has a psychological effect 
upon the consumers and tends to reduce complaints due to 
auto-suggestion. 

The most important advantage of the process is the 
elimination of the aftergrowth problem. At Denver, where 
the aftergrowth trouble is possibly more acute than at any 
other city on the continent, it was effectively banished by 
the use of chloramine. At Ottawa, the sanitary significance 
of B. coli aftergrowths is no longer of practical interest because 
such aftergrowths have ceased to occur. Whatever may be 
their opinion as to the sanitary significance of aftergrowths, 
all water sanitarians will agree that the better policy is to 
prevent their occurence. 

Operation of Chloramine Frocess. For the successful 
operation of the chloramine process, the essential factors 
are low concentrations of the hypochlorite and ammonia 
solutions. The author has found that hypochlorite containing 
0.3-0.5 per cent of available chlorine and ammonia contain- 
ing 0.3-0.5 per cent of anhydrous ammonia can be mixed in a 
4:1 or 8 : 1 ratio without appreciable loss in titre. Solu- 
tions of these concentrations mixed in 4 : 1 ratio lost only 
2-3 per cent of available chlorine in fifteen minutes and less 
than 10 per cent in five hours. The effect of mixing solutions 
containing 4.35 per cent of available chlorine and 2.2 per 
cent of ammonia is shown in Table XXX. 

The stability of chloramine is a function of the concentra- 
tion and the temperature and in practice it will be found 
advisable to determine in. the laboratory the maximum con- 
centrations that can be used at the maximum temperature 
attained by the water to be treated (cf . Muspratt and 
Smith 6 ). 



CHLORAMINE 



127 



According to Raschig l two competing reactions occur 
when ammonia is in excess. 

(i) NH 2 C1+NH3 = N2H 4 HC1 hydrazine hydrochloride 
and (2) 3NH 2 C1+2NH 3 = N2+3NH 4 C1. 

When the excess of ammonia is large, as on the addition 
of ammonia fort, the second reaction predominates and the 
yield of nitrogen gas is almost quantitatively proportional 
to the quantity of available chlorine present. As ammonium 
chloride has no germicidal action, and hydrazine a carbolic 
coefficient of only 0.24 (Rideal), the formation of these com- 
pounds should be avoided. 

TABLE XXX.— LOSS ON MIXING HYPOCHLORITE AND AMMONIA 

Hypochlorite containing 4.35 per cent available chlorine. Ammonia contained 

2.2 per cent NH 3 





Loss of Available Chlorine After 


Weight. 


Few Minutes. 


1 Hour. 


24 Hours. 


6 : 1 

4 : 1 
2 : 1 
1 : 1 
1 : 2 


Per cent 
19 
24 

45 
9i 
20 


Per cent 
19 
25 
47 
91 
28 


Per cent 
19 
25 
47 
92 

65 



The dosage of chloramine can be checked by titration 
of the available chlorine (see p. 82) immediately after treat- 
ment or by the estimation of the increment in the total 
ammonia (free and albuminoid). Routine determinations 
of the latter made in Ottawa show that practically the whole 
(90-95 per cent) of the added ammonia can be recovered by 
distillation with alkaline permanganate and that 85-90 per 
cent is in the " free " condition. 



128 • CHLORINATION OF WATER 

In operating the chloramine process it is important that 
the pipes used for conveying the chloramine solution should 
be of ample dimensions and provided with facilities for 
blowing out the lime that deposits from the solution. 

Ca(OCl)2 + 2NH 3 = 2NH 2 Cl+Ca(OH) 2 . 

The marked activity of chloramine as a chlorinating agent 
could be predicated from its heat of formation, which is 
8,230 calories. The other possible chloramines should be 
even more active as the heat of formation of these com- 
pounds are: 

Dichloramine NHCI2 — 36,780 calories. 

Nitrogen trichloride NCI3 — 65,330 calories. 

Dichloramine is unknown but nitrogen chloride has been 
prepared and is a highly explosive yellow oil that decomposes 
slowly when kept under water in the ice box. NCI3 can be 
easily prepared by passing chlorine gas into a solution of 
ammonium chloride and this process would suggest that a 
method might be found of utilising chlorine and ammonia 
as gases for the production of nitrogen trichloride as a germi- 
cide for water chlorination. NH4Cl+3Ci2 = NCl3-f-4HCl. 

The " available" chlorine content of the chloramines is 
double the actual chlorine content as each atom of chlorine 
will liberate two atoms of iodine from hydriodic acid. 

NH2CI + 2HI = I 2 +NH4CI. 
NCI3+6HI =3l 2 +NH 4 Cl-r-2HCl. 

Halazone 

For the sterilisation of small individual quantities of water, 
such as are required by cavalry and other mobile troops, 
bleach and acid sulphate tablets have been usually employed. 



CHLORAMINE 129 

Such tablets have given fairly satisfactory results but certain 
difficulties inherent to these chemicals have made it desirable 
to seek other methods. 

The subject was investigated by Dakin and Dunham. 7 
who first tried chloramine-T (sodium toluene-^-sufphochlora- 
mide). It was found that heavily contaminated waters, 
and particularly those containing much carbonates, required 
a comparatively high concentration of the disinfectant: 40 
parts per million of chloramine-T were necessary in some 
cases and such an amount was distinctly unpalatable. By 
adding tartaric acid or citric acid the effective concentration 
could be reduced to 4 p.p.m. but the mixture could not be 
made into a tablet without decomposition and a two-tablet 
system was deemed undesirable. 

Toluene sulphodichloramines were next tried. Excellent 
bacteriological results were obtained but the manufacture of 
tablets again presented difficulties. When the necessary 
quantity of dichloramine was mixed with what were assumed 
to be inert salts — sodium chloride for example — the normal 
slow rate of decomposition was accelerated. The dichlora- 
mine, in tablet form, was also found to be too insoluble to 
effect prompt sterilisation. 

The most suitable substance found by Dakin and Dun- 
ham was "halazone" or ^-sulphodichloraminobenzoic acid 
(C^N-C^S-CeELi-COOH). This compound is easily pre- 
pared from cheap readily available materials and was found to 
be effective and reasonably stable. 

The starting point in the preparation of halazone is 
^-toluenesulphonic chloride, a cheap waste product in the 
manufacture of saccharine. By the action of ammonia, 
^-toluene sulphonamide is produced and is subsequently 
oxidised by bichromate and sulphuric acid to ^-sulphonamido- 
benzoic acid. This acid, on chlorination at low temperatures, 
yields p-sulphondichloraminobenzoic acid (halazone). The 
reactions may be expressed as follows: 



130 



CH 3 



CHLORINATION OF WATER 
COOH 



S0 2 -NH 2 



S0 2 -NH 2 



COOH 



S0 2 -NC1 2 



Halazone is a white crystalline solid, sparingly soluble 
in water and chloroform, and insoluble in petroleum. It 
readily dissolves in glacial acetic acid from which it crystal- 
lizes in prisms (M.P. 213 C). 

The purity of the compound can be ascertained by dis- 
solving in glacial acetic acid, adding potassium iodide, and 
titrating with thiosulphate ; 0.1 gram should require 14.8 
to 14.9 c.cms. of N/10 sodium thiosulphate. Each chlorine 
atom in halazone is equivalent to 1 molecule of hypochlorous 
acid and the "available" chlorine content is consequently 
52.5 per cent or double the actual chlorine content. 

>S02-NCl 2 +4HI=>S0 2 -NH 2 + 2HCl+2l 2 . 

From the bacteriological results given by Dakin and 
Dunham it would appear that 3 parts per million of halazone 
(1.5 p.p.m. available chlorine) are sufficient to sterilise heavily 
polluted waters in thirty minutes and that this concentration 
can be relied upon to remove pathogenic organisms. 

The formula recommended for the preparation of tablets 
is halazone 4 per cent, sodium carbonate, 4 per cent (or dried 
borax 8 per cent), and sodium chloride (pure) 92 per cent. 

Halazone and halazone tablets, when tested in the author's 
laboratory on the coloured Ottawa River water seeded with 
B. coli, have given rather inferior results. With 1 tablet per 
quart, over six hours were required to reduce a B. coli content 
of 100 per 10 c.cms. to less than 1 per 10 c.cms. Clear well 
waters gave excellent results and large numbers of B. coli 
were reduced to less than 1 per 10 c.cms. in less than thirty 
minutes. McCrady * has also obtained excellent results 

* Private communication. 



CHLORAMINE 131 

with various strains of B. coli seeded into the colourless St. 
Lawrence water. 

BIBLIOGRAPHY 

i) Raschig. Chem. Zeit, 1907, 31, 926. 

2) Rideal. S. J. Roy. San. Inst., 1910, 31, 33-45. 

3) Race. J. Amer. Waterworks Assoc, 1918, 5, 63. 

4) Race. Eng. and Contr., 191 7, 47, 251. 

5) Contract Record. Aug. 15, 191 7, 696. 

6) Muspratt and Smith. J. Soc. Chem. Ind., 1898, 17, 529. 

7) Dakin and Dunham. Brit. Med. Jour., 1917, No. 2943, 682. 



CHAPTER X 
RESULTS OBTAINED 

The object of adding chlorine or chlorine compounds to 
water is for the purpose of destroying any pathogenic organ- 
isms that may be present. In a few instances some collateral 
advantages are also obtained but, in general, no other object 
is aimed at or secured. 

Chlorination does not change the physical appearance of 
water; it does not reduce or increase the turbidity nor does 
it decrease the colour in an appreciable degree. 

The chemical composition is also practically unaltered. 
When bleach is used there is a proportionate increase in the 
hardness but the amount is usually trifling and is without 
significance. During 1916 when the Ottawa supply was 
entirely treated with bleach at the rate of 2.7 parts per mil- 
lion (0.92 p.p.m. of available chlorine) the average increase in 
the total hardness as determined by the soap method was 
2.5 parts per million. 

When chlorine is added to prefiltered water, as an adjunct 
to filtration, an increase in the number of gallons filtered per 
run has been noted at some plants. This increase is not so 
great with rapid as with slow sand filters but in some instances 
it has led to appreciable economies. 

Walden and Powell l of Baltimore, found that the addi- 
tion of a quantity of bleach equal to approximately 0.50 
p.p.m. of available chlorine enabled the alum to be reduced 
from 0.87 to 0.58 grain per gallon. The percentage of water 
used in washing the filters was also reduced, from 4. 1 per cent 

132 



RESULTS OBTAINED 133 

to 2.9 per cent, whilst the filter runs were increased on the 
average by one hour and ten minutes. The net saving in 
coagulant alone amounted to 30 cents per million gallons. 

Clark and De Gage 2 found that the use of smaller amounts 
of coagulant during the period of combined disinfection and 
coagulation resulted in ah increase of nearly 25 per cent in 
the quantity of water passed through the filter between 
washings, and also in a material reduction of the cost of 
chemicals, which averaged $2.62 per million gallons for 
combined disinfection and coagulation as against $4.86 for 
coagulation alone. The water used in these experiments 
was obtained from the Merrimac River at Lawrence. 

The effect of hypochlorite on the reduction of algae growths 
on slow sand filters was first noticed by Houston during the 
treatment of the Lincoln supply in 1905. Two open service 
reservoirs were fed with treated water and were themselves 
dosed from time to time. " Previous to 1905 they developed 
seasonally most abundant growths, but during the hypo- 
chlorite treatment it was noticed that they remained bright, 
clear, and remarkably free from growths " (Houston 3 ). 

Ellms, 4 of Cincinnati, has also noted the effect of hypo- 
chlorite on algae. When the bleach was added to the coagu- 
lated water the destruction of the plankton was not as satis- 
factory as had been anticipated and it was found that large 
doses destroyed the coating of the sand particles and rendered 
the filters less efficient. The use of bleach in the filtered 
water basin was more successful and cleared it of troublesome 
growths. 

In 191 6, during the treatment of the London Supply 
with bleach (dosage 0.5 p.p.m. of available chlorine), Houston 
made further observations on this point. The Thames water, 
taken at Staines, had previously been stored for considerable 
periods in reservoirs, but this necessitated lifting the water 
by pumps which consumed large quantities of coal that were 
urgently needed for national purposes. As a war measure, 



134 CHLORINATION OF WATER 

the storage was eliminated and the water treated with hypo- 
chlorite at Staines and allowed to flow by gravitation to the 
various works where the slow sand filters are situated. The 
treatment resulted in a marked reduction in the growths of 
alga?, the reduction in the area of filters cleaned in 1916 
(June to September) as compared with 1915 being as follows: 

Percentage 
Filter Works. Reduction 

(Approximate). 

Grand Junction (Hampton) 6 

Grand Junction (Kew) 43 

East London (Sunbury) 30 

Kempton Park ^^ 

West Middlesex 56 

A portion of this reduction can probably be attributed 
to the elimination of storage. 

Chlorination, by decreasing the load on filter beds, has 
enabled the rate of filtration to be increased in some cases. 
This increased capacity, which would otherwise have neces- 
sitated additional filter units, has been obtained without any 
further capital outlay. At Pittsburg (Johnson 5 ) the rate of 
filtration, after cleaning, was increased 250,000 gallons each 
hour until the normal rate was reached; restored beds were 
maintained at a 250,000 gallon rate for one week. After the 
introduction of chlorination it was found possible to increase 
the rates more rapidly without adversely affecting the purity 
of the mixed filter affluents. 

Hygienic Results. Evidence as to the actual reduction 
of the number of such pathogenic germs as B. typhosus in 
water supplies by chlorination is most readily found in the 
death rates from typhoid fever in cities that have no other 
means of water purification. In some cases this evidence 
is necessarily of a circumstantial nature; in others it is 
definite and conclusive. 

Some of the earlier results of the effect of chlorination on 
typhoid morbidity and mortality rates were compiled by 



RESULTS OBTAINED 



135 



Jennings 6 and others have been published by Longley. 7 
These data have been brought up to date in Table XXXI 
and other statistics added. 



TABLE XXXI.— EFFECT OF CHLORINATION ON TYPHOID RATES 

Average Typhotd Death Rate Per 100,000 Population 



City. 



Baltimore 

Cleveland 

Des Moines 

Erie 

Evanston, 111. . . 

Jersey City 

Kansas City, Mo 
Omaha, Neb. . . . 

Trenton 

Montreal 

Toronto 

Ottawa 



Com- 
menced 
Chlorina- 
ation. 



June 191 1 
Sept. 191 1 
Dec. 1910 
Mar. 191 1 
Dec. 191 1 
Sept. 190S 
Jan. 1911 
May 1 9 10 
Dec. 191 1 
Feb. 1910 
Apr. 191 1 
Sept. 191 2 



Before Using. 



Period. 



1900-10 
1900-10 
1905-10 
1906-10 
1908-n 
1900-17 
1900-IO 
1900-09 
1907-II 
1906-10 
1906-10 
1906-10 



Rate. 



After Using. 



Period. Rate 



1912-15 
1912-16 
1911-13 
1912-14 
1912-13 
1909-16 
1911-16 
1911-16 
1911-14 
1911-16 
1912-16 
1913-17 



Percentage 
Reduction. 



36 

77 
41 
70 

5° 
55 
66 

53 
35 
37 
75 
50 



The figures given in this table show the effect of chlori- 
nation only; no other form of purification was used during 
the periods given, except at Toronto where a portion of the 
supply has been subjected to filtration. 

It will be seen that since chlorination was adopted the 
typhoid death rates have been reduced by approximately 
50 per cent and that the averages for the period after treat- 
ment are almost invariably less than 20 per 100,000, a figure 
that a few years ago was regarded as satisfactory. The 
average death rate for the last available year is 11 per 100,000, 
a result that is even more satisfactory and exceeds the antici- 
pations of the most optimistic of sanitarians. 

A portion of the reduction in the typhoid rates is no doubt 
due to improvements in general sanitary conditions but the 
reduction is much greater than can be accounted for in that 



136 



CHLORINATION OF WATER 



manner alone and in many cases there was a sharp decline 
immediately following the commencement of chlorination. 

In a few instances there is evidence that chlorination 
has reduced the typhoid rates of cities previously supplied 
with filtered water. Diagram X, drawn from data supplied 
by Dr. West, of the Torresdale Filtration Plant, shows the 
effect of disinfecting the filter effluents at Philadelphia. 



DIAGRAM X 

TYPHOID IN PHILADELPHIA 



100 
90 

, 80 
! 70 

( 

!■ 

i 60 

I 

! 50 

I 
I 

i 40 

' 30 

20 

10 





































i 





L 














/ 




/ 




filtered-. 

chlorinatt 










P 


r: ° i ; i ; 

ircentage of water 































i 
i 


>■ — < 


> — c 


* 


/ 






































l 




































{ 


! 




































J 






































1 

i 






























Y 


! 






i 
i 






























/' 






i 


\ 






























i 






/ 






























s 


> 






/ 




































































/ 


































,i 


v ; 


( 




c 


f 
































































f' 



























100 
00 
80 
70 
60 
50 
40 
30 
20 



,1897 1898 1899 1900 1901 1902 1903 1901 1905 1906 1907 1908 1909 1910 1911 1912 1913 1911 1915 191G 

Year 



During the years 1909-10-n, when practically the whole 
of the city supply was filtered, the average typhoid death rate 
was 18, but when the water was also chlorinated, in 1914-15- 
16, the rate was only 7, a reduction of 61 per cent. 

The figures in Table XXXII show that the Torresdale 
niters, during 191 5-16 were unable to adequately purify the 
water and that chlorination was necessary. 



RESULTS OBTAINED 



137 



TABLE XXXIL— CHLORINATION OF FILTER EFFLUENTS 

(Torresdaxe) 



Oxygen 

Con- 
sumed. 



Colour. 



Turbidity. 



Bacteria Per Cubic Centimeter. 



Untreated. 



Gelatine. 



Agar. 



Treated. 



Gelatine. 



Agar. 



1915 
1916 



I. 70 
I.90 



0.6 

Nil. 



141 



30 
23 



28 
38 



14 





B. coli communis 
Per Cent Positive Tests. 






Untreated. 


Treated. 


Added Chlorine 
Parts Per Million. 




10 c.cms. 


1 c.cm. 


10 c.cms. 


1 c.cm. 




1915 

1916 


66 
49 


24 
16 


5 
7-4 


0-3 
1.9 


O.18 
O.I5 



In Diagram XI the typhoid death rates of Columbus, 
Ohio, and New Orleans are shown to exemplify conditions 
that have not been improved by chlorination. The endemic 
condition of typhoid in Columbus was brought to an abrupt 
conclusion by the installation and operation of the softening 
and filter plant in September, 1908, and no further reduction 
followed the introduction of chlorination in December, 1909. 

In New Orleans the typhoid rate decreased on the incep- 
tion of the new water works system in 1909 and again after 
the installation of the Carroll ton filters in 191 2. The product 
of the filtration plants has always been above suspicion but 
aftergrowths occasionally developed and the bacterial count 
then exceeded the United States Treasury standard. To 
overcome this difficulty, hypochlorite was used in 19 15, but, 
as was anticipated, it had no effect on the typhoid rate. The 
high rate in New Orleans is largely due to outside cases received 
for hospital treatment and to other circumstances beyond 
the control of the water and sewerage department. 



138 



CHLORINATION OF WATER 



In all the examples previously cited, the evidence as to 
the effect of chlorination on typhoid mortality rates is cir- 
cumstantial but, taken as a whole, it is fairly conclusive. 
In the examples to be considered next the evidence is more 
direct. 

One of the most conclusive experiments as to the bene- 
ficial effect of chlorination is that reported by Young 8 of 

DIAGRAM XI 

TYPHOID IN COLUMBUS AND NEW ORLEANS 




1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 

Year 

Chicago. The water supply of Chicago was obtained from 
Lake Michigan by means of intake pipes and pumped to 
various parts of the city. The distribution system was 
divided into four districts and, although there was a certain 
amount of mixing along the borders, the water supplied to 
each district was substantially separate. The rapid and 
progressive decline in the typhoid rate of Chicago (from 19.8 



RESULTS OBTAINED 



139 



in 1900 to 10.8 in 191 1) subsequent to the diversion of the city 
sewage from the lake, led to the assumption that water-borne 
typhoid had ceased to be of any moment. Early in 1912, 

DIAGRAM XII 

AUTUMNAL INCREASE IN TYPHOID, CHICAGO (Young) 



140 

130 
120 
110 

. 100 

s 

90 
S 

-o 

1 80 

'ft 

>> 

% 70 

1 60 

u 

o 

bo 

ci 

§ 40 
o 

u 

* 30 

20 

10 





















1 








3 : 








i-t 








1 


i 




1 


I 




■ 




s 


1 


■ 




3 










i 


1 







C2 








I 


I 


c 

c 




OS 


















Si 


as 














OS 


































1912 










District 1. 

Chlorinated 

Water 


District 2. 
Eaw Water 


District 3. 
Raw Water 


District 4. 
Raw Water 



however, permission was secured to chlorinate the supply 
of one district (No. 1) and the treatment was continued until 
December when the solutions commenced to freeze Diagram 



140 



CHLORINATION OF WATER 



XII shows the effect of the treatment on the autumnal 
increase in District No. i as compared with the other three 
districts. The autumnal increase was calculated from the 
excess of typhoid incidence for July to November inclusive, 
over that for February to June inclusive. 

These results demonstrate in a most striking manner the 
beneficial effect of chlorination. The general conditions, 
with the exception of the raw water supply, were approxi- 
mately the same in all four districts. Diagram XIII shows 

DIAGRAM XIII 

B. COLI IN CHICAGO RAW WATER (Young) 



District No. 


Percentage of samples 
containing B. coli in 1 c.cm. 
5 10 15 20 






1 
















2 ' ' 






















3 












4 





that the raw water supply of District No. i was slightly worse 
than any of the others, 21.8 per cent of the samples from 
District No. 1 containing B. coli in 1 c.cm. as compared with 
21.0 per cent in the most polluted supply of the other districts. 
The results obtained at Ottawa are also conclusive. Fol- 
lowing two epidemics of typhoid fever in 191 1 and 19 12, 
caused by breaks in the intake pipe, hypochlorite treatment 
was commenced and has been in continuous operation until 
February, 1917, when chloramine treatment was substituted. 
The dosage has been so regulated as to assure a high degree 
of purity at all times in the water delivered to the mains 
and as evidence of this it might be mentioned that the average 



RESULTS OBTAINED 



141 



B. coli index (calculated by Fhelps' method) for the years 
1916 and 1917 was only 0.27 per 100 c.cms. The typhoid 
rates for the five years preceding the epidemic years and for 
a similar subsequent period are given in Diagram XIV. 

The diagram shows that there has been a constant reduc- 
tion in the city typhoid rate since the last severe epidemic 
with the exception, of the year 1915. The high rate of that 

DIAGRAM XIV 
TYPHOID IN OTTAWA 

















Legreo 


. Tota'l Rate 








d C\ty 


Rate 




■" 


















// 




)\ 

\\ 
1 \ 
1 \ 






















1 

1 
1 

1 
1 
1 

I 


V 

"S 


\ \ 
1 1 
\ \ 

1 V 


iloiina 


;Ion co 


nmenc 


3d 














1 


















/ 1 


\\ 






1 




i\ 














/ / 


\ \ 
\ \ 






li 




\\ 














/ / 


\ \ 






1 




\ \ 
\ \ 














{ 


\ \ 




V 






\\ 
















\ 




_— <■ 




1 




V 




















1 


) 




\ 
































s 


























x 




























~^-~< 


) — 



1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1911 



year was caused by a localised epidemic started by polluted 
well water and spread by flies from an unsewered area. This 
outbreak was the cause of about seven deaths registered 
during that year (population ico,coo). 

The objection might be raised that if the reduction of the 
typhoid rate were due to the water treatment, the decline 
should have been abrupt and not a gradual one. It is probable 
that there has been practically no water-borne typhoid in 



142 



CHLORINATION OF WATER 



the city since chlorination was commenced but this fact is 
masked by cases from other sources. During 1911 and 1912 
over 3,500 cases of typhoid were reported, of which an appre- 
ciable number would become carriers for various periods of 
time. As these carriers decreased the number of cases 
infected by them would also decrease and so account for a 
gradually declining death rate. 

It might be further objected that the reduced typhoid 
rate is due to a general improvement in the sanitary condi- 
tions. If the death rate from causes other than typhoid 
can be regarded as a measure of the general sanitary conditions 
it is obvious from the data in Table XXXIII that the improve- 
ment in the typhoid rate is immeasurably greater than can be 
ascribed to that cause. 

TABLE XXXIII.— DEATH RATES IN OTTAWA BEFORE AND AFTER 
CHLORINATION 



Cause. 



Rate Per 100,000 



1908-12 1913-17 



Percentage 



Reduction 



Increase 



Total * 

Typhoid, total 

Typhoid, city 

Pneumonia 

Tuberculosis 

Diarrhoea and Enteritis under 2 years. . . 



14.90 

34t 
26 f 

100 

133 
i39 



14.78 
17 
8 

107 

138 

128 



1. 2 

5° 
69 



7.0 

3-7 



* Rate per 1,000. t 1906-10, epidemic years 1911-12 excluded. 

One further objection might be made : that the raw water 
was not infected during 1913-17 Or infected to a smaller 
extent than during the previous period. Attempts to isolate 
B. typhosus from the raw water have invariably been futile 
but their presence in 1914 might be inferred from the fact 
that during the latter part of the summer of that year an 
epidemic of typhoid fever occurred at Aylmer, a village that 
discharges its sewage into the Ottawa River about six miles 
above the Ottawa intake. Hull, situated on the opposite 



RESULTS OBTAINED 143 

bank of the river and having a population of 20,000, takes 
its water supply from the same channel that supplies Ottawa 
but at a point a few hundred feet further down stream. Dur- 
ing November and December, 1914, some 200 cases of typhoid 
fever (incidence 1,000 per 100,000) occurred in Hull as com- 
pared with 28 in Ottawa. As the Ottawa intake is situated 
between the Hull intake and the outlet of the Aylmer sewer 
it is incredible that the Ottawa raw water was not also infected. 

In 1916 a liquid chlorine plant was installed in Hull, 
but in 191 7, owing to an accident, it was out of commission 
for a short period and at least 100 cases of fever developed 
during the following month. During the same period only 
two cases were reported in Ottawa and of these one was 
obviously contracted outside the city. 

In view of the preceding facts it must be granted that the 
improvement in the typhoid rate of Ottawa can be definitely 
attributed to an improvement in the water supply caused by 
chlorination. 

The efficacy of chlorination to prevent and check epidemics 
of water-borne typhoid has never been doubted. Innumer- 
able instances could be cited in which the prompt treatment 
of large public supplies has promptly checked outbreaks that 
threatened to assume serious proportions and there is no 
doubt that the extremely low typhoid morbidity rate on the 
Western Front of the European battlefield is partially due to 
the extensive and rigorous chlorination measures that have 
been instigated. Prophylactic vaccination and the prompt 
isolation of typhoid carriers have largely contributed to the 
wonderful results obtained but due credit must also be given 
to the systematic purification and treatment of water sup- 
plies. Similar results have been obtained at training camps 
in Canada and in other countries by effective treatment 
with either liquid chlorine or hypochlorite. 

Since the inception of water chlorination in America in 
1908, the merit of the method has been very generally recog- 



144 CHLORINATION OF WATER 

nized throughout the Continent but was regarded with 
scepticism in Europe, except as a temporary expedient, until 
the results obtained by the military forces compelled more 
general recognition. Before the war, chlorination of water 
supplies in England was only practised in a few isolated and 
relatively unimportant instances; in 1917, practically the 
whole supply of London was chlorinated and at Worcester a 
similar treatment has been recommended to enable the slow 
sand filters to be operated at higher rates without reducing 
the quality of the water supplied to the consumers. 

Use and Abuse of Chlorine. Inasmuch as chlorination has 
no beneficial effect on water except the reduction of the 
bacterial content it should be used for this purpose only and 
under such conditions as permit the operations to be under 
full control at all times. The supplies that can be most 
efficiently and safely treated are those that are relatively 
constant in chemical composition and bacterial pollution. 
Changes in volume can be dealt with by automatic apparatus 
but sudden changes in organic and bacterial content require 
a change of dosage that cannot be made by any mechanical 
appliance. Long experience and accurate meteorological 
records may in some cases enable those in charge of chlori- 
nation plants to anticipate changes in the conditions of the 
water supply, but it is always preferable to provide a positive 
method of preventing sudden changes by using chlorination 
merely as an adjunct to other processes of purification. 
Unpurified waters that are objectionable on account of their 
bacterial content only are very rare, as the cause that pro- 
duces the bacterial pollution usually produces other con- 
ditions that are equally objectionable though not so danger- 
ous to health. Sudden storms in summer, or sudden thaws 
in winter, usually cause large increments in turbidity accom- 
panied by soil washings that often carry appreciable quan- 
tities of faecal matter into surface water supplies. Lake 
supplies often suffer in the same manner and sewage, which 



RESULTS OBTAINED 145 

during normal conditions is carried safely away from water 
intakes, obtains access to the supply. If the dosage is main- 
tained at a level sufficiently high to meet these abnormal 
conditions, complaints as to taste and odour would ensue, 
and in general, such a practice is impossible. Some sup- 
plies have been chlorinated successfully for years but the 
principle of using chlorination as the first and last line of 
defence cannot be recommended. Success can only be 
obtained by eternal vigilance and the responsibility for results 
is more than water works officials should be called upon to 
assume. 

Chlorination is an invaluable adjunct to other forms of 
water purification and it is not improbable that, in the future, 
filter plants will be designed to remove aesthetic objections 
at the lowest possible cost and that chlorination will be 
relied upon for bacterial reduction. Chlorination is the 
simplest, most economical, and efficient process by which 
the removal of bacteria can be accomplished and there is no 
valid reason why it should not be used for that purpose. 

The popularity of this process has suffered through the 
efforts of over zealous enthusiasts who have been unable 
either to recognize its limitations or to appreciate the fact 
that a domestic water supply should be something more than 
a palatable liquid that does not contain pathogenic organisms. 
Every system of water purification has its limited sphere of 
utility and chlorination is no exception to the rule. 

BIBLIOGRAPHY 

(i) Weldon and Powell. Eng. Rec, iqio, 61, 621. 

(2) Clark and De Gage, 41st Annual Rpt. Mass. State B. of H. iqio. 

(3) Houston. 12th Research Rpt. Metropolitan Water Board, London. 

(4) Ellms. Eng. Rec, 191 1, 63, 388. 

(5) Johnson. Eng. Rec, ion, 64, No. 16. 

(6) Jennings. 8th Inter. Congr. Appl. Chem., 26, 215. 

(7) Longley. J. Amer. Waterworks Assoc, 191 5, 2, 679. 

(8) Young. J. Amer. Public Health Assoc, 1914, 4, 310. 



APPENDIX 



ESTIMATION OF CHLORINE IN CHLORINATED WATERS 

Reagents, i. Tolidine solution. One gram ®f 0- tolidine, 
purified by recrystallization from alcohol, is dissolved in 
i litre of 10 per cent hydrochloric acid. 

2. Copper sulphate solution. Dissolve 1.5 grams of cop- 
per sulphate and 1 c.cm. of concentrated sulphuric acid in 
distilled water and dilute the solution to 100 c.cms. 

3. Potassium bichromate solution. Dissolve 0.025 gram 
of potassium bichromate and 0.1 c.cm. of concentrated sul- 
phuric acid in distilled water and dilute the solution to 
100 c.cms. 

Procedure. Mix 1 c.cm. of the tolidine reagent with 
100 c.cms. of the sample in a Nessler tube and allow the solu- 
tion to stand at least five minutes. Small amounts of free 
chlorine give a yellow and larger amounts an orange colour. 

For quantitative determination compare the colour with 

that of standards in similar tubes prepared from the solutions 

of copper sulphate and potassium bichromate. The amounts 

of solution for various standards are indicated in the following 

table : 

147 



148 



CHLORINATION OF WATER 



PREPARATION OF PERMANENT STANDARDS FOR CONTENT 
OF CHLORINE 



Chlorine. 


Solution of 
Copper Sulphate. 


Solution of 
Potassium Bichromate. 


Parts per million. 


c.cms. 


c.cms. 


O.OI 


O.O 


0.8 


.02 


O.O 


2.1 


• 03 


0.0 


3-2 


.04 


O.O 


4-3 


•OS 


0.4 


5-5 


.06 


0.8 


6.6 


.07 


I . 2 


7-5 


.08 


i-5 


8.7 


.09 


i-7 


9.0 


.10 


1.8 


10. 


. 20 


1.9 


20.0 


•3° 


1.9 


30.0 


.40 


2.0 


38.0 


•So 


2.0 


45 -o 



APPENDIX 



149 



DIAGRAM XV 

Orifice Discharges 



II 
■a 


* 


" 


1 


* *B / 
II 1 

"is/ 


" 1 




'1/ 
V 




k/ 

V 































































































500 



1000 1500 2000 2500 3000 

U.S. Gallons per 24_Hours 



DIAGRAM XVI 



3500 4000 4500 

For Imperial Gallons Deduct J*ij 



Bleach and Chlorine Dosage percenta s e oi A 7 a i\ ab i? o Ch,0rlne in BIeach 

^30 31 32 33 31 35 30 3? 38 nn 




0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 .1.1 1.2 
Available Chlorine in Treated Water, Parts per Million 



NAME INDEX 



Adams, 66, 82 

Bassenege, 9 
Baxter, 4 
Berge, 9 
Berthollet, 1 
Bevan, 29 
Bon jean, 36 
Bray, 24 
Breteau, 26 
Bucholtz, 5 

Catlett, 99 
Clark, S3, 133 
Comte, 47 
Cross, 29 
Cruikshank, 3 



B 



D 



Dakin, 22, 28, 129 
Darnall, 89 
Davy, 1 

DeGage, 53, 133 
DeMorveau, 3 
Dibden, 6 
Dienert, 48 

Dienheim-Brochoki, 105 
Dowell, 24 
Dunbar, 6 
Dunham, 129 
Dupre, 5 
Dusch, 4 

E 
Ellms, 34, 83, 84, 133 
Elmanovitsch, 36 



G 



Eisner, 6 
Evans, 84 

Faraday, 103 
Fischer, 16 
Forcrand, 103 
Fuller, G. W., n 

Gascard, 47 
Griffen, 17, 79 

H 
Haberkorn, 5 
Hale, 80, 100 
Harrington, 34, 65 
Hauser, 83, 84 
Hedallen, 17, 79 
Heise, 36 
Henry, 2 
Hermite, 5 
Hewlett, 9 
Hooker, 72 
Horrocks, 48 
Houston, 8, 59, 71, 133 
Hsu, 21 

J 

Jackson, 91, 99 
Jakowkin, 26 
Jennings, 135 
Johnson, n, 134 
Jordan, H. E., 57 



K 



Kanthdack, 6 
Kauffman, 9 
Kellerman, 7 



151 



152 



NAME INDEX 



Kershaw, 107 
Kienle, 65, 66, 90, 99 
Kimberly, 7 
Klein, 5 
Koch, 4 

Kolessnikoff, 16 
Kranejuhl, 7 
Kuhn, 5 
Kurpjuivat, 7 

L 
Landolt, 105 
Langar, 10 
Laroche, 47 
Lavoisier, 1, 15 
Leal, 16 
Lehmann, 101 
LeRoy, 83 
Letton, 64 
Longley, 43, 135 
Lunge, 105 
Lyon, 24 

M 
Marshall, 102 
Massy, 48 
Meadows, 112, 114 
McCrady, 130 
McGowan, 8 
McLintock, 5 
Mohler, 31 
Mohr, 79 
Moor, 9 
Muspratt, 126 



Nesfield, .8, 89 
Nissen, 30 
Norton, 21 
Novey, 23 
Noyes, 24 

Ornstein, 90 
Orticoni, 36 

Pedler, 103 
Percy, 3 
Pettenkofer, 101 



N 



O 



Phelps, 7, 17, 82 
Pitcher, 112 
Plucker, 10 
Powell, 132 
Pratt, 7 
Proskauer, 6, 16 

R 

Rabs, no 

Race, 36, no, 116 

Raschig, 115 

Rickard, 108 

Rideal, E. K, 84 

Rideal, S., 6, 9, 21, 22, 60, 115, 116 

Roscoe, 5 

Roozeboom, 103 

Rouquette, 36 

Ruffer, 5 

S 
Sandman, 56 
Scheele, 1, 15 
Schemmelweiss, 4 
Schroder, 4 
Schuder, 10 
Schumacher, 7 
Schumburg, 10 
Schwann, 4 
Schwartz, 7 
Sickenberger, 9 
Smeeton, 53 
Smith, 126 

T 
Tennant, 2 
Thomas, 53, 56 
Thresh, 87 
Tiernan, 92 
Tolman, 11 1 
Traube, 9 

V 
Valeski, 36 
Von Loan, 90 



W 



Walden, 132 
Walker, 87 
Wallace, 92 y 



NAME INDEX 



153 



Wallis, 83 
Warouzoff, 16 
Watt, 2, 3, 15, 106 
Webster, 5, 105 
Wesb rook, 31, 44, 53 
West, 91, 99, 136 
Whittaker, 31 
Winkler, 84 



Winogradoff, 16 
Winslow, no 
Woodhead, 7 
Woolf, 5 

Young, 138 

Zirn, 6 



Y 

Z 



SUBJECT INDEX 



Absorption of chlorine by water, 35 
Abuse of chlorination, 144 
Acids, effect of, 19, 21 
Action of chlorine, 16 
Admixture, effect of, 39 
Aftergrowths, 55 

accelerated growth, 58 

B. coli in, 57 

effect of liquid chlorine, 99 

views as to nature of, 56 
Algffi, effect of chlorine on, 133 
Alkalies, effect of, 19, 20 
Allen-Moore cell, in 
Ammonia, and chlorine, 24 

and sodium hypochlorite, 114 

effect on bleach, 21 

effect on oxidising action, 21 

soda process, 2 
Antichlors, 86 
Antiseptics, early work on, 3 

chlorine as an, 50 
Application of chlorine, point of, 43 
Auto-suggestion, 62 

B 

B. cholera suis, 31 

B. cloaca, 31 

B. coli, aftergrowths, 57 

in sewage, 6, 7 

in water, 9, 28, 31 

standard, 46 

viability of, 52, 55 
B. cuticidaris, 53 
B.fcecalis alkaligenes, 31 



B. enter itidis, 31 
B. enteritidis sporo genes, 53 
B. lactis Trogenes, 31 
B. subtilis, 53 
B. tetani, 9 

B. typhosus, 9, 10, 30, 31 
Bacteria surviving chlorination, 50 
aftergrowths, 55 
nature of, 53 
spores, 57 
Benzidine, 83 

Bleach, analysis of solution, 79 
as deodourant, 3, 6 
as sewage disinfectant, 6, 7 
at Adrian, n 
at Boonton, 11, 16 
at Bubbly Creek, n 
composition, 14 
decomposition of, 25 
discovery, 2 

germicidal velocity, 20, 21 
hydrolysis, 18, 19 
production, 3 
stability of, 17 
toxic action, 22 
treatment, 72 
control of, 78 
cost, 86 

dosage regulation, 75 
in France, 78 
losses in, 81 
mixing tank, 73 
plant design, 72 
storage tank, 75 
Brest experiments, 5 



155 



156 



SUBJECT INDEX 



Carnallite, i 

Chicago, typhoid rate, 138 
Chloramine, 114 
at Denver, 124, 126 
at Ottawa, 28, 116 
contact period, 123 
cost of, 124 
decomposition of, 126 
experimental results, 119 
germicidal power, 116 
operation of process, 126 
plant design, 1 20 
preparation of, 115 
ratio of chlorine and ammonia, n5, 

122 
tastes and odours, 28, 64, 117 
toxic action, 22, 29 
Chlorides, effect of, 20 
Chlorine, and ammonia, 24, 25 
discovery of, 1 
disinfection, effect of pabulum, 4 

general reactions, 28 
hydrate, 103 
detection of, 81 
effect on flowers, 68 
estimation of, 81 
.in sanitary work, 4 
medicinal dose, 67 
oxygen equivalent, 23 
liquid, 89 

advantages of, 97 

cost of treatment, 101 

disadvantages of, 101 

germicidal efficiency, 99 

machines, 89 
peroxide, 9 
water, 102 

corrosion of pipes, 69 

damage to seeds, 68 

decomposition of, 15 

heat of formation, 27 
Chlorometer, 84 
Chloros, 8 
Chlorozone, 105 



Colour, effect on dosage, 33 
Columbus, typhoid rates, 137 
Complaints, 62 
Contact period, effect on dosage, 44 

effect on taste, 43 

usual practice, 45 
Cost of bleach plant, 85 

bleach treatment, 86 

liquid chlorine treatment, 101 
Crossness experiments, 5 

D 

Dayton cell, 107 

DeChlor filters, 87 

Denver, chloramine treatment, 124, 

126 
Dichloramine, 128 
Disinfectants, 50 
Disinfection, early views of, 3 
Dosage, 30 

determination of, 46 
effect of, admixture, 39 
colour, 33 
contact period, 43 
initial contamination, 32 
light, 45 

oxidisable matter, 32 
standard of purity, 30, 32 
temperature, 34, 36 
turbidity, 45 
for military work, 48 
regulation of bleach, 75 
relation to oxygen absorbed, 36 
tanks, 75 



Eau de Javelle, 3, 47 

Electrical conductivity of treated 

water, 70 
Electrolysed sea water, 5 
Electrolytic hypochlorite, 2, 104 

Bradford, 5 

Brest, 5 

Brewster, 6, 105 

cost of, 113 



SUBJECT INDEX 



157 



Electrolytic hydrochlorite, Cross- 
ness, 5 

discovery of, 3 

diaphragm cells, no 

early use of, 5 

efficiency of, 109 

Havre, 5 

non-diaphragm cells, 106 
Electrozone, Brewster, 6 

Maidenhead, 6 

Tonetta Creek, 6 



Filter effluents, chlorination of, 34 
Filters, effect on beds, 60 

effect on runs, 132 
Fish, effect on, 8, 67, 68 



Germicidal velocity, effect of acids, 2 1 

alkalies, 20 

ammonia, 21 

chlorides, 20 
Guildford, chlorination at, 9 

H 

Haas and Oettel cell, 108 

Halazone, 128 

Hardness, effect of chlorine on, 132 

Havre experiments, 5 

Hermite fluid, 5 

Hexamethyl-^-aminotriphenylme- 

thane, 83 
Historical, 1 
Hooghly River, 7 
Hydrazine, 126 
Hydrogen peroxide, 24 
Hydrolysis of hypochlorites, effect of, 

acids, 19 

alkalies, 19 

chlorides, 20 
Hygienic results, 134 
Hypochlorous acid, 17 

decomposition of, 24, 25, 26 
hydrolytic constant, 18 



Initial contamination, effect on dos- 
age, 32 
Intestinal organisms, viability of, 52 
Iodoform taste, 65 
Iron salts, effect on dosage, ^^ 



Jersey City, court case, n, 16 
K 



Kellner cell, 10S 



Labarraque solution, 105 
Leavitt- Jackson machine, 91 
Leblanc process, 2 
Light, effect on dosage, 45 
Lincoln, chlorination at, 8, 59 
Liquid chlorine, advantages of, 97 
and tastes, 65 

effect of temperature on, 95 
machines, 89 

dry feed, 94 

E. B. G. Co., 91 

Leavitt- Jackson, 91 

operation of, 95 

Wallace and Tiernan, 92 
L'Orient, experiments at, 5 

M 
M. agilis, 53 

Maidstone, use of bleach at, 8 
Margin of safety for taste and odour, 

64 
Material for bleach plants, 74 
Military work, bleach method for, 78 

chlorine water, 103 

dosage for, 47, 48, 78 

early European, 10 

liquid chlorine, 102 

typhoid reduction, 143 

use of chlorine in, 8 
Mixing tank for bleach, 73 



158 



SUBJECT INDEX 



Moisture, effect on chlorine gas, 16 
Montreal, dosage at, 34 
electrolytic cells, 112 

N 
Nascent oxygen hypothesis, 17 
Nelson cell, in 
Neva River, 36 

New Orleans, typhoid rates, 137 
New York, bacteria surviving treat- 
ment, S3 

bleach efficiency, 100 

liquid chlorine plant, 97 
Nitrites, effect on dosage, 33 
Nitrogen trichloride, 24, 128 

O 

Odours, effect of contact period on, 43 

nature of, 63 
Ottawa, aftergrowths at, 57 

bleach plant efficiency, 100 

chloramine plant, 120 

chloramine results, 121 

sludge trouble, 65 

typhoid rates, 140 
Oxidisable matter, effect on dosage, 

32, 36 
Oxychloride, Guildford, 9 

Middlekerke, 9 

Ostend, 9 
Ozone, 24 

P 
Philadelphia and chlorination, 136 
Pipe corrosion, 69 

Pittsburg report, 71 
Plumbo-solvency, 71 
P. mirabilis, 31 
Potassium permanganate, 23 
Puerperal fever in Vienna, 4 
Pumps, for admixture, 41 

R 

Red Bank, sewage disinfection at, 7 
Reversed ratio of counts, 54 



Sewage disinfection at Baltimore, 7 

Berlin, 7 

Boston, 7 

Brewster, 6 

Hamburg, 6 

Maidenhead, 6 
Sludge, as cause of complaints, 65 
Sodium bisulphite, 86 
Sodium chloride, deposits, 1 

decomposition of, 106 
Sodium hypochlorite, 105 

decomposition of, 26 

effect of ammonia on, 21 

hydrolysis of, 26 
Sodium thiosulphate, 87 
Standard of purity, 30 
Storage tanks, 75 
Sulphuretted hydrogen, 33 
Sylvine, 1 

T 
Tannin, 67 
Tastes, effect of contact period on, 43 

nature of, 63 
Temperature, effect on absorption of 
chlorine, 35, 38 

bleach deterioration, 72 

dosage, 34, 36 

germicidal velocity, 38 

pressure of liquid chlorine, 96 

tastes and odours, 66 
Thermophylic organisms, 54 
Tolidine, 82 

Toxic action of chlorine, 22, 29 
Turbidity, effect on dosage, 45 

effect of chlorine on, 132 

U 
Use of chlorination, 144 

W 

Water mains, disinfection of, 8 
Well water, 7 

Worcester, chlorination at, n 
Worthing experiments, 5 



